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Objective: To evaluate potential associations between concentrations of antimüllerian hormone (AMH) and T as well as the LH/FSH ratio and the unbiased precise ovarian volume obtained after unilateral ovariectomy., Design: Cohort study., Setting: University hospital., Patient(s): A total of 765 patients having one ovary surgically removed for fertility preservation. Inclusion criteria were age >15 years and ovarian volume <25 mL; 386 women had one or more hormone parameter (AMH, LH, FSH, or total T) determined before oophorectomy., Intervention(s): None., Main Outcome Measure(s): A precise weight of the ovary was equated with ovarian volume. Associations between ovarian volume and AMH, the LH/FSH ratio, T concentrations, and body mass index (BMI) were evaluated. Patient characteristics in relation to ovarian volume cutoff values between 8 and 12 mL were also examined., Result(s): Ovarian volume was significantly positively associated with concentrations of AMH, the LH/FSH ratio, and T. Ovarian volume, concentrations of AMH and LH, and the LH/FSH ratio were significantly augmented in women having ovarian volumes above a threshold of 8, 9, and 10 mL compared with those below. Average age, FSH, and T concentrations did not differ between below and above the 10 mL threshold. There was a significant association between BMI and ovarian volume and BMI and T, while other hormone parameters were nonsignificant., Conclusion(s): The precise ovarian volume reflected ovarian activity measured as circulating concentrations of AMH and T as well as the LH/FSH ratio. These significant associations showed continuous progression, and a 10 mL threshold offered no clear difference compared with other volume threshold values., (Copyright © 2019 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

In vertebrates, the regulation of gametogenesis is under the control of gonadotropins (Gth), follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh). In fish, the physiological role of Gths is not fully understood, especially in species with asynchronous ovarian development. To elucidate the role of Gths in species with asynchronous ovary, we studied European hake (Merluccius merluccius) during the reproductive season. For this aim, we first cloned and sequenced both hormones. Then, we characterized their amino acid sequence and performed phylogenetic analyses to verify the relationship to their orthologues in other species. In addition, the quantification of gene expression during their natural reproductive season was analyzed in wild-caught female hake. Our results revealed that fshb peaked during the vitellogenic phase, remaining high until spawning. This is in contrast to the situation in species with synchronous ovary. lhb, on the other hand, peaked during maturation as it is also common in species with synchronous ovarian development. Finally, combining double-labeling fluorescent in situ hybridization (FISH) for Gth mRNAs with immunofluorescence for Lh protein, we evidenced the specific expression of fshb and lhb in different cells within the proximal pars distalis (PPD) of the pituitary. In addition to gonadotrope cells specific to expression of either fshb or lhb, some cells showed co-expression of both genes. This suggests either that gonadotropes with co-expression are not yet specified or they could have a plasticity that permits changes from one cell phenotype to another during certain life stages and in turn during different physiological states., (© 2017 Society for Reproduction and Fertility.)

The incidence of obesity is increasing rapidly all over the world and results in numerous health detriments, including disruptions in reproduction. However, the mechanisms by which excess body fat interferes with reproductive functions are still not fully understood. After weaning, female rats were treated with a cafeteria diet or a chow diet (control group). Biometric and metabolic parameters were evaluated in adulthood. Reproductive parameters, including estradiol, progesterone, LH and prolactin during the proestrus afternoon, sexual behavior, ovulation rates and histological analysis of ovaries were also evaluated. Cafeteria diet was able to induce obesity in female rats by increasing body and fat pad weight, which resulted in increased levels of triglycerides, total cholesterol, LDL and induced insulin resistance. The cafeteria diet also negatively affected female reproduction by reducing the number of oocytes and preantral follicles, as well as the thickness of the follicular layer. Obese females did not show preovulatory progesterone and LH surges, though plasma estradiol and prolactin showed preovulatory surges similar to control rats. Nevertheless, sexual receptiveness was not altered by cafeteria diet. Taken together, our results suggest that the cafeteria diet administered from weaning age was able to induce obesity and reduce the reproductive capability in adult female rats, indicating that this obesity model can be used to better understand the mechanisms underlying reproductive dysfunction in obese subjects., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The corpus luteum (CL) plays a central role in the maintenance of pregnancy in rodents, mainly by secreting progesterone. Female mice lacking prolactin (PRL) receptor (R) are sterile due to a failure of embryo implantation, which is a consequence of decreased luteinizing hormone (LH) receptor expression in the CL and inadequate levels of progesterone. We attempted to treat PRLR(-/-) females with human chorionic gonadotropin (hCG) and showed a de novo expression of LHR mRNA in the corpora lutea. Binding analysis confirmed that the LHR in hCG-treated PRLR(-/-) animals was functional. This was accompanied with increased expression of steroidogenic enzymes involved in progesterone synthesis. Despite these effects, no embryo implantation was observed because of high expression of 20alpha-hydroxysteroid dehydrogenase. To better appreciate the molecular mechanisms underlying maintenance of the CL, a series of mRNA expression-profiling experiments was performed on isolated corpora lutea of PRLR(-/-) and hCG-treated PRLR(-/-) mice. This approach revealed several novel candidate genes with potentially pivotal roles in ovarian function, among them, p27, VE-cadherin, Pten, and sFRP-4, a member of the Wnt/frizzled family. This study showed the differential role of PRL and LH in CL function and identified new targets of these hormones in luteal cells.

Chronic exposure to oestrogens is known to inhibit the secretion of luteinising hormone (LH) in rats, leading to anovulation. Hypothalamic catecholamines, norepinephrine and dopamine play an important role in LH regulation. However, the effects of chronic exposure to low levels of oestradiol on hypothalamic catecholamines have not been investigated thoroughly. In the present study, adult female Sprague-Dawley rats were either sham implanted or implanted with 17beta-oestradiol (E(2)) pellets (20 ng/day) for 30 (E-30), 60 (E-60) or 90 (E-90) days. E(2) exposure affected oestrous cyclicity and ovarian morphology in a duration-dependent manner. There was no change in oestrous cyclicity in E-30 rats; however, 75% of E-60 and 95% of E-90 rats were acyclic (P < 0.05). Cycling rats from E-30 or the control group were killed at different time points on the afternoon of pro-oestrous. E-30 rats in oestrous, constant oestrous rats in the E-60 and E-90 groups and a group of old constant oestrous (OCE) rats were killed at 12.00 h. LH was measured in the serum by radioimmunoassay. Individual hypothalamic nuclei that are involved in LH regulation were microdissected and analysed for norepinephrine and dopamine levels using high-performance liquid chromatography/electrochemical detection. Norepinephrine levels in the hypothalamic nuclei increased significantly in control and E-30 groups during the afternoon of pro-oestrous, which was accompanied by a rise in LH levels (P < 0.05). On the day of oestrous, norepinephrine concentrations in hypothalamic nuclei and serum LH were significantly lower in E-60, E-90 and OCE rats compared to E-30 and control rats. On the other hand, dopamine levels declined significantly in one hypothalamic nucleus. These results indicate that chronic E(2) exposure affects hypothalamic catecholamine and serum LH levels in a duration-dependent manner. This coincides well with the loss of cyclicity observed in these animals. These results suggest that repeated exposure to endogenous oestrogens could play a role in reproductive senescence.

Background: The current study was designed to determine if follitropin alfa (recombinant human follicle-stimulating hormone; r-hFSH) and lutropin alfa (recombinant human luteinizing hormone; r-hLH) biopotencies were unchanged by reconstituting in sterile water for injection and mixing prior to injection., Methods: The biopotencies of r-hFSH and r-hLH were determined following injection of female Sprague-Dawley rats with a mixture of follitropin alfa revised formulation female (RFF) and lutropin alfa (1:1, r-hFSH:r-hLH). Biopotencies of follitropin alfa RFF and lutropin alfa were measured using ovarian weight and ascorbic acid depletion assays, respectively, and compared with a reference standard. Stock mixtures of follitropin alfa RFF and lutropin alfa (1:1) were prepared within 1 h prior to each respective assay's injection and stored at 6 +/- 2 degrees C. Separate low dose (follitropin alfa RFF 1.5 IU/rat, lutropin alfa 2 IU/rat) and high dose (follitropin alfa RFF 3 IU/rat, lutropin alfa 8 IU/rat) treatments were prepared from stock mixtures or individual solutions by diluting with 0.22% bovine serum albumin saline solution and injected within 1 h of preparation. The main outcome measures were ovarian weight and ovarian ascorbic acid depletion., Results: FSH bioactivities were similar (p > 0.10) between the individual follitropin alfa RFF test solution (84.2 IU) and follitropin alfa RFF/lutropin alfa (87.6 IU) mixtures prepared within 1 h of injection and stored at 6 +/- 2 degrees C. LH bioactivities were similar (p > 0.10) between lutropin alfa (94.7 IU) test solution and lutropin alfa/follitropin alfa RFF (85.3 IU) mixtures prepared within 1 h of injection and stored at 6 +/- 2 degrees C for not more than 1 h prior to injection., Conclusion: Mixing follitropin alfa RFF and lutropin alfa did not alter the bioactivity of either FSH or LH.

Female mutant restricted ovulator (RO) chickens of the White Leghorn strain carry a naturally occurring single nucleotide mutation in the very low density lipoprotein receptor (VLDLR) gene. Due to this mutation, RO hens fail to express a functional VLDLR protein on the oocyte membrane, which results in an impaired uptake of circulating yolk precursor macromolecules. Mutant RO hens subsequently develop hyperlipidemia and generally fail to lay eggs due to follicular atresia. Since RO hens also reportedly have three-fold higher basal plasma estrogen concentrations, combined with four-fold lower levels of circulating progesterone as compared to wild-type (WT) hens, we hypothesized that RO hens would have an increased abundance of pituitary progesterone receptor (PR) mRNA and PR isoforms A and B as well as alterations in circulating gonadotrophin levels. Quantitative PCR assays revealed significantly greater (P

In various adult teleost fishes, LH ovulatory peak is under a dual neurohormonal control that is stimulatory by GnRH and inhibitory by dopamine (DA). We investigated whether DA could also be involved in the inhibitory control of LH at earlier steps of gametogenesis by studying the model of the European eel, Anguilla anguilla, which remains at a prepubertal stage until the oceanic reproductive migration. According to a protocol previously developed in the striped bass, eels received sustained treatments with GnRH agonist (GnRHa), DA-receptor antagonist (pimozide), and testosterone (T) either alone or in combination. Only the triple treatment with T, GnRHa, and pimozide could trigger dramatic increases in LH synthesis and release as well as in plasma vitellogenin levels and a stimulation of ovarian vitellogenesis. Thus, in the prepubertal eel, removal of DA inhibition is required for triggering GnRH-stimulated LH synthesis and release as well as ovarian development. To locate the anatomical support for DA inhibition, the distribution of tyrosine hydroxylase (TH) in the brain and pituitary was studied by immunocytochemistry. Numerous TH-immunoreactive cell bodies were observed in the preoptic anteroventral nucleus, with a dense tract of immunoreactive fibers reaching the pituitary proximal pars distalis, where the gonadotrophs are located. This pathway corresponds to that mediating the inhibition of LH and ovulation in adult teleosts. To our knowledge, this is the first demonstration of a pivotal role for DA in the control of LH and puberty in a juvenile teleost. These data support the view that DA inhibition on LH secretion is an ancient evolutionary component in the neuroendocrine regulation of reproduction that may have been partially maintained throughout vertebrate evolution.

The purpose of this study was to determine the occurrence of and the regulatory mechanisms involved in priming of the pituitary to GnRH before the preovulatory LH surge in sheep. Experiment 1: Forty-two ewes had progestagen devices removed after 14 days and were assigned to luteal (Lut) or follicular (Foll) groups. Fifteen days later, blood sampling was initiated either immediately or 36 h after induced luteolysis in groups Lut and Foll, respectively. After 4 h, ewes were administered either saline (n = 5) or 250 ng (n = 8) or 10 microg (n = 8) of GnRH. Five ewes per treatment group were killed 1 h later, while remaining animals were blood sampled for a further 7 h. Experiment 2: Eighteen ewes were allocated to Lut and Foll groups (described above). Blood samples were collected from 2 h before GnRH (10 microg) treatment until 7 h after. Despite up-regulated GnRH-R mRNA levels in Foll ewes, pituitary content and plasma levels of LH and LHbeta mRNA levels were similar between groups. Mean FSHbeta mRNA and plasma FSH levels were elevated in Lut ewes but declined after GnRH treatment. Inversely, plasma estradiol and inhibin-A concentrations were higher in Foll ewes and declined after GnRH treatment. Fewer LH(+ve)/secretogranin II(-ve) (SgII(-ve)) granules were present in gonadotropes of Foll ewes, coincident with increased basal LH levels. Fewer smaller sized granules were present after GnRH treatment. In conclusion, there was no evidence of self-priming before onset of the preovulatory LH surge. Constitutive release of LH(+ve)/SgII(-ve) granules may maintain basal LH levels while smaller sized, presumably mature granules may be preferentially released after GnRH stimulation.

Androgens, in addition to serving as a substrate for estrogen biosynthesis, exert autocrine/paracrine actions on ovarian function. However, much of the information regarding the actions of androgens on the ovary has been obtained using rodents, and the extent to which these results can be extrapolated to higher primates is uncertain. The current study was initiated to determine the effects of dihydrotestosterone (DHT) and testosterone (T) on the responsiveness of the rhesus monkey ovary to exogenous FSH and LH in vivo. Rhesus monkeys whose spontaneous gonadotropin secretion was interrupted with a GnRH antagonist received s. . implants of either DHT or T for 5 d before and continuing throughout a 15-d i.v. infusion of human FSH and LH. Neither T nor DHT treatment synergized with FSH/LH to stimulate estrogen production or increases in ovarian weight. Rather, administration of DHT significantly reduced estrogen secretion and the augmentation of ovarian weight in response to exogenously administered FSH and LH. These results indicate that high concentrations of DHT are antagonistic to gonadotropin-stimulated ovarian function in primates.

Background: Fetal growth restraint has been associated with FSH hypersecretion in early infancy and in early post-menarche, and with reduced uterine and ovarian size in adolescence. It is unknown whether these reproductive anomalies persist, respectively, into late infancy and into the reproductive age range., Methods: We report follow-up findings in two age groups of girls. A cohort of infants [n=26; n=10 born appropriate-for-gestational-age (AGA) and n=16 born small-for-gestational-age (SGA)], who had been studied at the age of approximately 4 months, was assessed again at the age of 12 months. A cohort of teenagers (n=28), who had been studied at the age of approximately 14 years, was assessed again at the age of approximately 18 years; this group was complemented by a transversal cohort of similar age (n=19) for a total of 47 young women (n=27 AGA; n=20 SGA). In infants, only serum FSH was measured; adolescents underwent endocrine-metabolic screening, ultrasound assessment of uterine-ovarian size, and evaluation of body composition by dual X-ray absorptiometry., Results: Serum FSH levels were higher in SGA than AGA infant girls at 4 and 12 months, and higher in SGA than AGA adolescents at 14 and 18 years (all P<0.01). Longitudinal ultrasound assessments disclosed a late-adolescent increment of uterine size that was less obvious in SGA than AGA girls. In contrast, ovarian volume remained stable in both subgroups. Compilation of longitudinal and transversal results at 18 years of age corroborated the persistent reduction in the uterine size of SGA girls (by approximately 20%; P<0.005) and in their ovarian volume (by approximately 40%; P<0.0001); moreover, SGA girls displayed not only a persistent elevation of FSH (by approximately 50%; P<0.001), but also a rise of LH and fasting insulin, as well as an excess of abdominal fat (all P<0.01)., Conclusions: The gynaecology of young women born SGA was found to be characterized by hypergonadotrophinaemia and by a reduced uterine and ovarian size.

Egg laying begins in domestic hens, reared on short daylengths, at about day 147 of age and is advanced by photostimulation after but not before about day 42 of age. The development of this response at day 42 may be facilitated by oestrogen. This hypothesis was investigated in prepubertal hens, reared on short daylengths, by comparing the effects of oestrogen treatment on pituitary and plasma FSH and LH responses to photostimulation (16 h light:8 h dark) for 1 week at days 34 and 54 of age. Oestradiol benzoate (0.5 mg kg(-1)) was injected i.m. on alternate days for 1 week before and after photostimulation. At day 34, pituitary LH content increased after photostimulation but plasma LH and FSH concentrations did not increase. At day 54, pituitary FSH content and plasma FSH and LH concentrations increased after photostimulation, whereas pituitary LH content did not increase. At days 34 and 54, oestrogen treatment decreased pituitary FSH and LH contents but did not block the stimulatory effect of photostimulation on pituitary FSH. At day 34 but not at day 54, photostimulation combined with oestrogen treatment increased plasma FSH and LH concentrations. Plasma LH but not plasma FSH concentration increased after GnRH-I injection at days 34 and 54. These observations are consistent with the hypothesis that, in prepubertal female chickens, maturation of the neuroendocrine mechanism mediating photoinduced FSH and LH release may be mediated by oestrogen. This effect of oestrogen on photoinduced LH release may be mediated by increased GnRH-I release or enhanced pituitary responsiveness to GnRH-I. It is proposed that neuroendocrine mechanisms controlling photoinduced FSH release may involve oestrogen-responsive interactions between pituitary paracrine factors, including activins and follistatin.

In turkey hens, the egg production rate is relatively high early during a reproductive period, but declines as the period progresses. Among lines with different egg production potential, the interval between preovulatory surges of LH is the primary determinant of the egg production rate. The main objective of this study was to determine whether the decline in egg production rate late during an egg production period is also associated with a difference in the interval between LH preovulatory surges. A group of photosensitive turkey hens (Early) were photostimulated with continuous light (24L:0D) at 40 wk of age to induce egg laying, and serial blood samples were collected after about 3 wk of egg production. A second group of hens (Late) were housed in floor pens and photostimulated with 14L:10D at 40 wk of age for a normal 36-wk reproduction period and were then switched to 24L:0D lighting for 2 wk before collection of serial blood samples. Continuous light photostimulation was used for at least 2 wk before and during serial blood sampling to avoid potential masking effects of diurnal lighting on the interval between LH surges. The Early (n = 12) and Late (n = 16) hens were cannulated 3 days before being serially bled hourly for 10 days. The mean interval between preovulatory surges of LH was shorter in the Early hens than in the Late hens (26.1 +/- 2.5 h and 34.7 +/- 3.9 h, respectively). The intra-hen LH surge interval coefficient of variation was lower in the Early hens than in the Late hens (7.2% and 18.6%, respectively). The inter-hen LH surge interval coefficient of variation was similar in the Early and Late hens (9.5% and 11.2%, respectively). The incidence of blind surges of LH (those not retrospectively associated with ovipositions) was not different between Early and Late laying hens (8.4% +/- 15.2% and 7.3% +/- 14.6%, respectively). In conclusion, in turkey hens, longer intervals and greater intra-hen variation between LH surges were associated with a poorer rate of egg production late in the reproductive period relative to early in the reproductive period.

The fourth International Standard for Human Urinary FSH and LH (IS; in ampoules coded 98/704) was compared with the third International Standard for Urinary FSH and LH (IS 71/264) by 10 laboratories in nine countries, using FSH and LH in vivo bioassays. Estimates of the FSH content of the IS by augmented ovarian weight gain assays were homogeneous within each laboratory and over all laboratories. The combined weighted geometric mean estimate of FSH content of the IS (with 95% fiducial limits) in terms of IS 71/264 was 71.9 (69.0-74.9) IU/ampoule. Although estimates by seminal vesicle weight gain (SVW) assays of the relative LH activities of the IS and IS 71/264 were homogeneous within laboratories, estimates were heterogeneous between laboratories. This indicated differences between the spectrum of LH isoforms in the IS and IS 71/264, which were obtained from different manufacturers, and differences between the specificities of SVW assays performed in different laboratories. The differences between the specificities of SVW assays appeared to be related to interactions among mean laboratory seminal vesicle weights, age and genetic strain of rat. The finding of inter-laboratory differences in the specificities of SVW assays is of some significance, as this assay method has been generally adopted by Pharmacopoeias for the control of the LH content of therapeutic products. The combined unweighted geometric mean estimate of LH content of the IS (with 95% fiducial limits) in terms of IS 71/264 by SVW and ovarian ascorbate depletion assays was 70.2 (61.7-80.0) IU/ampoule. Estimates of the FSH and LH content of ampoules of the IS kept at increased temperatures suggested that the IS would be adequately stable under normal storage conditions. On the basis of these results, the World Health Organization Expert Committee on Biological Standardization established the preparation in ampoules coded 98/704 as the fourth International Standard for Human Urinary FSH and LH, and assigned to the contents of each ampoule an activity of 72 International Units of urinary FSH and an activity of 70 International Units of urinary LH.

Gonadal function is wholly reliant on the two pituitary-derived gonadotropins, FSH and LH. Identifying the specific effects of FSH has been difficult because of the intimate relationship between LH and FSH action and inherent limitations of classic research paradigms. We describe a novel transgenic model to characterize the definitive actions of FSH alone, distinct from LH effects, created by combining transgenic FSH expression with the gonadotropin-deficient background of the hypogonadal (hpg) mouse. A tandem transgene construct encoding each alpha- and beta-subunit of human FSH, under the rat insulin II promoter, expressed biologically active heterodimers at serum levels, by immunoassay, equivalent to circulating FSH concentrations in fertile humans (0.1-25 IU/liter). Transgenic mice were crossed into the hpg mouse genotype to obtain LH-deficient animals secreting FSH alone. Testis weights of adult FSHxhpg mice were increased up to 5-fold, relative to nontransgenic hpg controls (P < 0.001). However, only transgenic males with serum FSH levels more than 1 IU/liter showed testis weights increased relative to hpg controls, indicating a physiological FSH threshold for the testicular response. Histology of enlarged FSHxhpg testes revealed round spermatids and sparse numbers of elongated spermatids, demonstrating that the testosterone-independent FSH response targeting the Sertoli cell can facilitate completion of meiosis and minimal initiation, but not completion, of spermiogenesis. Transgenic FSH also induced inhibin B secretion in FSHxhpg mice, but showed a distinct sexual dimorphism with only females exhibiting a strong FSH dose-dependent increase in serum inhibin B levels (r(2) = 0.84). In addition, ovaries of FSHxhpg females were enlarged up to 10-fold (P < 0.001), characterized by increased follicular recruitment and development to type 7 antral follicles. Thus, these findings show that the transgenic FSHxhpg mouse provides a unique model for detailed investigations of the definitive in vivo actions of FSH alone.

A new superovulation regimen for the monovulatory brushtail possum (Trichosurus vulpecula) has been devised. It reduces the number of hormone treatments required and elicits a better rate of ovulation than the established pregnant mares' serum gonadotrophin (PMSG)-GnRH method. Ovarian stimulation was achieved by a single intramuscular injection of 15 iu PMSG. This treatment resulted in the recruitment and development of a large number (9-12) of Graafian follicles on the ovaries. Induction of ovulation was achieved by a single intramuscular injection of 2-10 mg pig LH or multiple intramuscular injections of GnRH, (4 x 50 micrograms, 90 min apart) given 72 h after PMSG treatment. Superovulation occurred in all animals (n = 48) examined 48 h after treatment irrespective of dose of LH or type of ovulatory stimulus used. The highest ovulatory success (83%), the maximum number of ovulation sites (9.5 +/- 2.8) and the highest number of oocytes recovered (9.0 +/- 2.5) were achieved after treatment with PMSG and 4 mg LH. These results were significantly greater than the ovulatory success (43%), numbers of ovulation sites (3.9 +/- 1.1) and number of oocytes recovered (2.1 +/- 0.9) after PMSG-GnRH treatment (P < 0.05). This simpler and more effective superovulation protocol should assist with more effective manipulation of possum reproduction in captivity.

The expression of LH receptor (LHR) mRNA was studied in fetal rat gonads using polymerase chain reaction multiplication of reverse-transcribed mRNA. A primer pair corresponding to the extracellular domain of the receptor revealed the expression of LHR mRNA in fetal ovaries and testes as early as embryonic Day 13.5, the earliest age studied. The localization of LHR mRNA was examined in the perinatal rat ovary using in situ hybridization with two antisense probes, one encoding the extracellular and the other encoding the transmembrane domains of LHR. At the age of 4 days, only the extracellular LHR probe gave specific signal over ovarian stromal and follicular cells, excluding the ova. Three days later, similar distribution of specific hybridization was observed with both probes. In the 10- and 30-day-old rat ovaries, clear expression of LHR mRNA was found to be with both probes in theca cells. Gonadotropin-stimulated production of cAMP was studied in cultures of dispersed perinatal rat ovarian cells. When 5-day-old ovarian cells were cultured for 3 days in vitro and then stimulated by either hCG (0.1 mg/L) or FSH (1 mg/L) for 6 h, cAMP production was enhanced only in cells stimulated by FSH. In a similar experiment with 7-day-old ovarian cells, cAMP production was stimulated by both FSH and hCG. Stimulation with hCG (0.1 mg/L) during the 3-day culture caused homologous desensitization of cAMP production, but stimulation with FSH (0.1 mg/L) had no such effect. The desensitization of the LHR was also investigated by treating neonatal rats in vivo with a high dose of hCG (600 IU/kg BW s.c. as a single injection on Day 7) or with a dosage of recombinant human (rec) FSH on Days 3-9 (0.3 IU s.c twice daily). Thereafter, at the age of 10 days, the ovaries were incubated either with recFSH (200 IU/L) or hCG (CR-121; 0.1 mg/L) for 1 h. Homologous desensitization of cAMP production by hCG was observed, but the FSH-mediated cAMP production was not affected. The hCG-induced steroidogenesis (progesterone and testosterone production) was not desensitized. In conclusion, these findings indicate that 1) the expression of the mRNA encoding the extracellular domain of LHR, i.e., truncated receptor, occurs in fetal rat gonads as early as embryonic Day 13.5; 2) the expression of the truncated LHR mRNA occurs uniformly in the differentiating ovarian cells before the appearance of the functional theca cell layer; 3) full-length LHR message appears in the developing ovary concomitantly with appearance of differentiated theca cells; 4) homologous desensitization of cAMP output by hCG, without steroidogenic desensitization, is present in perinatal rat ovaries; and 5) no FSH-evoked desensitization of cAMP production occurs in perinatal ovaries.

The objective of this study was to determine the influence of day length on gonadotropin profiles and the expression of their ovarian receptors in lactating sows. Primiparous Large White gilts were exposed to either a gradual increase (from 12 to 16 h/day, LONG treatment, n = 13) or decrease (from 12 to 8 h/day, SHORT treatment, n = 12) in photoperiod during gestation. Weaning occurred at Day 21 of lactation. All 4 sows that were submitted to the SHORT light duration and checked for postpartum estrus demonstrated an estrus by 10 days postwearing in contrast to 2 of 5 sows submitted to the LONG light duration (p < 0.05). In the remaining 16 sows, day length had no significant effect on the number of LH pulses or on mean or basal concentrations of gonadotropins (FSH and LH) or estradiol-17 beta measured at Day 20 of lactation. Ovarian receptors for gonadotropins and prolactin (PRL) and their mRNA were measured through use of receptor-binding and slot-blot analyses, respectively, at Day 21 of lactation in these 16 sows. ALONG photoperiod duration had no influence on receptor number, binding or affinity, but it significantly increased LH receptor mRNA levels (p < 0.05). However, FSH receptor mRNA levels were similar in the two groups of sows. Plasma LH concentration was positively related to LH and FSH receptor content but not to their cognate mRNA levels. Plasma concentration of FSH was positively related to the level of its own receptor mRNA as well as to that of the PRL receptor mRNA. Although the LONG day length may have delayed the return to estrus, there was no effect on gonadotropin secretion. Our results show an effect of photoperiod only on the level of LH receptor mRNA. We suggest that not all transcripts of the LH receptor are translated and that nontranslatable mRNA accumulate in ovaries of sows exhibiting delayed estrus.

'Pure' follicle stimulating hormone (FSH) and luteinizing hormone (LH) are expected shortly to become available for pharmaceutical use in the clinical setting. To test the contribution of LH to optimal ovarian responsiveness to FSH, 21-day-old hypophysectomized, immature, female rats received four s.c. injections of recombinant human LH (rhLH; total dose 1-10 IU) and/or rhFSH (total dose 30-72 IU) given at 12-hourly intervals. At 48 h after the first injection, ovaries were removed, weighed and used to isolate granulosa and thecal/interstitial cells for assessment of basal and gonadotrophin-responsive steroidogenesis in vitro, or homogenized to extract total RNA for Northern analysis of 17-hydroxylase/C17-20-lyase (cytochrome P-450c17 alpha) mRNA. Serum oestradiol and uterine weight were measured as indices of ovarian oestrogen production; androstenedione was measured to reflect ovarian androgen production. Consistent with the two-cell, two-gonadotrophin model of oestrogen synthesis, increased ovarian oestrogen secretion only occurred if both rhFSH and rhLH were given simultaneously. Treatment with rhFSH alone stimulated ovarian weight gain and granulosa cell aromatase activity without oestrogen secretion, whereas rhLH alone stimulated thecal androgen synthesis and androgen secretion. When the total rhLH dose was fixed at 1 IU, giving rise to an unmeasurably low serum concentration of rhLH, additional treatment with rhFSH (30-72 IU) dose-dependently stimulated serum androgen concentrations as well as oestrogen concentrations. The approximately 2.0 kb-sized P-450c17 alpha mRNA transcript was undetectable in the ovaries of untreated control animals but was abundant in the ovaries of positive controls treated with 15 IU of pregnant mare serum gonadotrophin.(ABSTRACT TRUNCATED AT 250 WORDS)

In 18-week-old nulliparous rabbit does, ovulation was induced with 50 IU of pure urinary luteinizing hormone (LH; LH group), or 50 IU of human chorionic gonadotrophin (HCG; HCG group), in order to determine the effect of these treatments on 17 beta-oestradiol and progesterone concentrations, and on oocyte and embryo quality. Luteinizing follicles, recovered oocytes, progesterone concentration and grade 5 embryos were significantly reduced when pure urinary LH was used. Statistically significant correlations were found: (i) between oestradiol concentration and number of degenerated oocytes in both groups (positive); (ii) between oestradiol concentration and grade 1 and 2 embryos (negative), and grade 5 embryos (positive) in the HCG group; (iii) between progesterone concentration and metaphase II oocytes (negative), and between progesterone and grade 5 embryos (positive), in the HCG group; and (iv) between progesterone and oestradiol concentrations (negative) in the LH group. It seems that the oestradiol to progesterone ratio improves during the early luteal phase when ovulation is induced with LH, and that oestradiol and progesterone concentrations could play a role in determining oocyte and embryo quality.

A potent LH-RH antagonist (Ac-D-Trp1,2, D-Cpa2, D-Lys6, D-Ala10 LH-RH (Antag) was used to study the differential regulation of FSH and LH secretion by endogenous LH-RH in ovariectomized (OVX) and regularly cycling rats. The endogenous LH-RH was suppressed by single injections of Antag in OVX animals and by long-term treatment with Antag in normal and OVX rats. Serum and pituitary LH and FSH, as well as serum estradiol (E2) and progesterone (P) was determined by RIA during and/or after the treatment. The direct effect of the antagonistic analog on the ovarian P release was tested in vitro using the isolated luteal cell system. Single injections of the Antag in OVX animals caused prompt and marked suppression of the serum LH (-80%), while no decrease of the serum FSH. Long-term treatment with the same analog decreased the serum LH by 50% but did not modify the serum FSH. In normal rats, serum LH dropped to undetectable levels, while serum FSH did not change significantly. Long-term treatment with the antagonist also resulted in divergent alterations in the pituitary gonadotropin concentrations. In OVX animals, the pituitary LH content moderately elevated (+21%), however, the FSH did not change. In normal rats, ovarian cycles were interrupted, and no ovulation appeared during the treatment. The pituitary LH concentration increased by 46%, while the FSH decreased by 43%. Marked depression was found in the serum P (-60%) but no significant change in the serum E2 levels. Incubation of isolated luteal cells with the Antag did not influence the HCG-induced P secretion in vitro, demonstrating that the in vivo inhibitory effect of the antagonistic LH-RH analog on the P secretion asserts not directly on the ovarian LH-RH receptors, but through inhibition of the endogenous LH-RH. Our studies give evidence that the long-term treatment with LH-RH antagonist suppress the LH and P but not the FSH and E2 secretion, and provide new data suggesting the presence of a FSH-releasing factor in the CNS.

LH, FSH, and TSH are heterodimeric glycoprotein hormones composed of a common alpha-subunit and unique beta-subunits. The alpha-subunit is produced in two distinct specialized cell types of the pituitary gland: gonadotropes, which synthesize LH and FSH, and thyrotropes, which synthesize TSH. We have demonstrated that 313 base pairs of the bovine-alpha subunit promoter direct expression of diphtheria toxin A chain specifically to the gonadotropes in transgenic mice. Animals carrying this transgene generally exhibit reproductive failure and lack of gonadal differentiation, consistent with gonadotrope ablation. Lack of gonadotrope activity was verified by RIA and immunohistochemical staining for LH. The phenotype of these transgenic mice is nearly identical to mice homozygous for the spontaneous mutation, hpg, which is due to a deletion in the gene encoding GnRH. Thyrotrope function was judged normal based on overall growth of the animals, appearance of their thyroids, T4 levels measured by RIA, and immunohistochemical staining for TSH. The ablation of gonadotropes but not thyrotropes suggests that separate cis-acting elements are necessary for expression of the alpha-subunit gene in these two cell types. Pituitary content of ACTH and GH was apparently normal, while PRL synthesis and storage were reduced. Thus, in a pituitary almost completely devoid of gonadotropes, most other pituitary functions were normal. This suggests that most pituitary cells are able to differentiate independently of terminal gonadotrope differentiation and can function in the absence of paracrine signaling provided by gonadotropes.

Ovaries from eCG-primed (20 IU s.c. on Day 28) rats were perfused from the morning of Day 30 of age in a recirculating system initially containing a buffered blood cell-free medium (M199 + 4% BSA) for periods of up to 21 h. The addition of ovine LH (0.1 micrograms/ml) at 0 h of perfusion resulted in ovulations in all 6 ovaries perfused (3.2 +/- 0.7 ovulations per treated ovary; mean +/- SEM), whereas none of the 6 control ovaries ovulated. Rat leukocytes (50 x 10(6)), added at 7 h of perfusion significantly increased the number of LH-induced ovulations (7.8 +/- 0.5; p less than 0.05). All ovulated oocytes showed resumption of meiosis as judged from the presence of germinal vesicle breakdown. Ovaries perfused with leukocytes but without LH did not ovulate. Histological examination of ovaries 14 h after leukocyte administration showed a considerable number of perifollicular extravasated white blood cells. These findings indicate that leukocytes participate in the normal ovulatory process as part of an inflammation-like reaction.

In order to determine the changes in the expression of LH beta messenger ribonucleic acid (mRNA) during GnRH agonist (GnRHa) treatment (0.94 mg/28 days), the concentration of the mRNA of LH beta was assessed together with the serum LH concentration, pituitary LH content and LH response to GnRH at various times during long-acting GnRHa treatment in immature female rats. The serum LH concentration was increased at hour 1, gradually decreased starting at approximately hour 3 and had returned to the control level on day 28. Pituitary LH began to decrease at hour 3. The concentrations of LH beta mRNA were not significantly different from those in the control group from hour 1 to hour 18, but were lower from day 3 to day 28. Serum LH response to native GnRH (1 micrograms) began to be inhibited on day 7. These results indicate that the short term treatment with GnRHa stimulates the release of preformed LH rather than synthesis of LH beta mRNA and that the long term treatment inhibited the expression of LH beta mRNA in a time dependent manner.

Photoperiodic response curves for LH release were obtained for juvenile female domestic chickens at 8 weeks of age by measuring changes in plasma LH concentrations after increasing the daily photoperiod from 8 to 10.5, 12.75, 15.25, 17.75 or 20 h. The birds were bred either for meat production (broiler) or commercial egg-laying and were fed ad libitum or a restricted diet, similar to that used under commercial conditions. Ovarian and oviduct growth was stimulated by 2 weeks after transfer to 20 h light/day in the dwarf broiler strain, irrespective of the dietary treatment, but not in birds of the egg-laying strain. Baseline concentrations of plasma LH were higher in the egg-laying than in the dwarf broiler strain birds. A significant effect of dietary treatment was observed on the changes in concentration of plasma LH in the nonphotostimulated dwarf broiler, but not in the egg-laying bird. There was no significant interaction between dietary treatment and photoinduced LH release in birds of either strain. The shortest photoperiod needed to stimulate LH release (critical daylength) was less than 10.5 h in the dwarf broilers and between 10.5 and 12.75 h in the egg-laying birds. The shortest photoperiod needed to stimulate the maximum release of LH (saturation daylength) was between 10.5 and 12.75 h in the dwarf broiler strain. The saturation daylength in birds of the egg-laying strain was longer, being between 12.75 and 15.25 h.(ABSTRACT TRUNCATED AT 250 WORDS)

The hypothesis tested was that the decline in negative feedback of estradiol on secretion of luteinizing hormone (LH) that occurs as puberty approaches in heifers results from a decline in the number of receptors for estradiol in the hypothalamus and/or pituitary. In addition, associated changes in receptors for luteinizing hormone-releasing hormone (LHRH) in the pituitary, ovarian follicle development, and uterine growth were characterized. Fifty prepubertal heifers, 234 to 264 days of age, were used. Six heifers of median body weight were designated controls, and sequential blood samples were collected at 20-min intervals for 24 h every 2 wk from 249 days of age through puberty and analyzed for concentrations of LH. Frequency of LH pulses/24 h was regressed on number of days prepuberty to develop a prediction equation for puberty. Thirty of the remaining 44 heifers were killed at 253, 302, and 351 days of age (n = 10/group), and tissues for described analyses were collected. Three to 5 days before tissue collection, sequential blood samples were obtained from these heifers, as described for control heifers to determine frequency of release of LH. With this information, number of days prepuberty at the time of tissue collection was estimated from the prediction equation developed with data from control heifers. The average age at puberty in control heifers was 366 days. The average age at puberty of heifers that were not killed or included in the control group (n = 14) was 360 days. Receptor and morphological data were related to the estimated onset of puberty. Cytosolic concentration of receptors for estradiol (fmoles receptor/mg cytosolic protein) in the anterior hypothalamus, medial basal hypothalamus, and anterior pituitary declined (p less than 0.05) as puberty approached. No change in concentration of receptors for estradiol was observed in the stalk median eminence or preoptic area. The concentration of receptors for LHRH in the anterior pituitary did not change as puberty approached. Uterine weight increased rapidly during the 50 days preceding puberty. The number of small, medium, or large follicles and the wet, pressed, or dry weight of the ovaries did not change as puberty approached. Follicles with a diameter greater than 12 mm were found only in the 3 heifers estimated to be closest to puberty at the time of tissue collection. The hypothesis that the decline in estradiol feedback on secretion of LH during the prepubertal period in heifers may result from a decline in the concentration of binding sites for estradiol at the hypothalamus and/or pituitary is supported by this study.

The effects of chronic adrenalectomy on the oestrous cycle, periovulatory gonadotrophin surges in sera and ovulation in the rat were assessed. Rats which were exposed to a 14 h light : 10 h darkness lighting schedule for at least 3 weeks and those which showed at least two consecutive 4 day oestrous cycles were divided into three groups. One group (controls) was left untreated. The rest were adrenalectomized (ADX) or sham-adrenalectomized (Sham) during oestrus and then placed in a different animal room with the same lighting schedule but with the onset and end of the photoperiod delayed by 4 h. These operations did not interrupt the length of the oestrous cycles. Rats were decapitated for collection of trunk blood on the fifth pro-oestrous or oestrous day after the operation. Both Sham and ADX rats synchronized to the new lighting schedule in terms of the temporal patterns of their periovulatory surges in serum LH and FSH and the timing of ovulation. Neither adrenalectomy nor the sham-operation altered the magnitude of the pro-oestrous or oestrous increases in serum LH or FSH when compared with those in control rats. Body, uterine and ovarian weights as well as the number of ova shed were similar in the ADX and Sham groups. The results indicate that adrenal secretions are not necessary for rats to synchronize the timing of the periovulatory surges in serum LH and FSH or ovulation to a 14 h light : 10 h darkness schedule and the periovulatory surges of LH and FSH are unaltered in chronically adrenalectomized rats.

Five lighthorse mares were actively immunized against gonadotropin releasing hormone (GnRH) to determine the relative importance of this hypothalamic hormone in the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Five mares immunized against the conjugation protein served as controls. Mares were initially immunized in November and received secondary immunizations 4 wk later, and then at 6-wk intervals until ovariectomy in June. All mares immunized against GnRH exhibited an increase (p less than 0.01) in the binding of tritiated GnRH by plasma, an indication that antibodies against this hormone had been elicited. Concentrations of LH, FSH and progesterone in weekly blood samples were lower (p less than 0.05) in GnRH-immunized mares than in controls after approximately 4 mo of immunization. However, the LH concentrations were affected to a greater degree than were FSH concentrations. All five control mares exhibited normal cycles of estrus and diestrus in spring, whereas no GnRH-immunized mare exhibited cyclic displays of estrus up to ovariectomy. All mares were injected intravenously with a GnRH analog (which cross-reacted less than 0.1% with the anti-GnRH antibodies) in May, after all control mares had displayed normal estrous cycles, to characterize the response of LH and FSH in these mares; two days later, the mares were injected with GnRH. The LH response to the analog, which was assessed by net area under the curve, was lower (p less than 0.01) by approximately 99% in mares immunized against GnRH than in control mares. In contrast, the FSH response to the analog was similar for both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Highly purified ovine FSH and LH were treated with neuraminidase to remove sialic acid and the desialylated derivatives were examined for biological activity in hypophysectomized immature male and female rats. The male rats were hypophysectomized at 22 days of age and beginning on day 25 were injected sc twice daily for 4 days with native or neuraminidase-treated FSH (total dose, 15 or 60 mug) or LH (12 mug). The ventral prostates, seminal vesicles, and testes were then removed and weighed, and serum testosterone levels were measured by radioimmunoassay. The female rats were hypophysectomized on day 28 and beginning on day 35 were injected sc twice daily for 4 days with native or neuraminidase-treated FSH (8 mug) or saline. On the morning of day 39, the rats were given an ovulating dose of gonadotropin (8 mug native or neuraminidase-treated FSH, or 1.28 mug native or neuraminidase-treated LH) or 1.0 ml saline iv via tail vein. Twenty-four hours later ova were counted in the oviducts the ovaries were weighed, and serum levels of progesterone and 20alpha-dihydroprogesterone were determined by radioimmunoassay. Treatment of ovine LH with neuraminidase did not diminish the ability of this hormone to increase prostate and testes weights and serum testosterone levels. Desialylation also did not decrease the ability of LH to induce ovulation. Although native ovine FSH significantly increased the weights of the ventral prostate, seminal vesicles, and testes, and elevated plasma testosterone levels, the desialylated derivative was essentially inactive. Neuraminidase treatment also eliminated the ability of ovine FSH to increase ovarian weight, to induce ovulation, and to elevate serum progesterone and 20alpha-dihydroprogesterone. These results indicate that the LH-like activity of ovine FSH is an intrinsic property of the FSH molecule.

Low doses (0.2 mg and 0.4 mg) of LH did not reveal any effect on the ovary of Puntius ticto (Ham.), but with 0.6 mg of LH the vitellogenesis began. Full maturation in the ovary was recorded with a total dose of 1.2 mg of LH and the fish spawned with a dose of 1.4 mg of LH.

In vivo experiments showed that anti-bovine luteinizing hormone rabbit serum (a-LH) reversed the abortifacient effect of Bromergocryptine (BEC) on day 6 of pregnancy in 13 of 19 rats when injected 5-15 h after the initial BEC administration. Radioreceptor assay studies revealed that BEC treatment entailed an 85% drop of ovarian LH-receptor (LH-rec) concentration and a drastic decrease in progesterone serum levels. a-LH restored both the ovarian LH-rec content and progesterone serum levels in those rats that were found to have macroscopically intact implantations. A time course study of LH serum levels after BEC treatment showed a trend for BEC to stimulate LH secretion with a maximum 12-18 h after the initial BEC injection. These experiments indicate that (i) BEC terminates early rat pregnancy primarily by inducing a process of desensitization of ovarian LH-rec by blocking prolactin (PRL) secretion and possibly also by additionally stimulating LH secretion, which in the absence of endogenous PRL causes HL-rec and serum progesterone levels to drop; (ii) a-LH administration without simultaneous PRL substitution may rescue LH-rec of BEC treated rats from being desensitized as well as prevent fetuses from being resorbed. It is suggested that the contribution of PRL in the luteotropic complex is permissive for the luteotropic action of LH and/or for keeping the corpus luteum in a functional state rather than being luteotropic by itself.

The objective of this study was to examine reproductive and endocrine changes in ewes actively immunized against a conjugation of luteinizing hormone (LH) and ovalbumin (LH immunized n = 10) or ovalbumin alone (control; n = 10). Ewes were immunized at weeks 0, 3 and 5 of the 93-week study and exposed to a fertile ram during weeks 7-25 (first breeding season) and weeks 60-67 (second breeding season). Immunization against LH abolished estrus and prevented pregnancy in all but one LH immunized ewe during the two breeding seasons. Uterine weights of LH immunized ewes were lighter than those observed in control ewes while ovarian weights did not differ between the treatment groups. No differences were observed between basal circulating concentrations of LH measured by an in vitro bioassay for the two treatment groups. However, serum concentrations of immunological follicle stimulating hormone, and the number of medium sized ovarian follicles (4-6 mm) were increased in LH immunized ewes. It was concluded from this study that immunization against LH prevents ovulation presumably by blocking the preovulatory surge of LH and not altering basal concentration of LH.

Overall, significantly more antral follicles greater than or equal to 1 mm diameter were present in Romney ewes during anoestrus than in the breeding season (anoestrus, 35 +/- 3 (mean +/- s.e.m.) follicles per ewe, 23 sheep; Day 9-10 of oestrous cycle, 24 +/- 1 follicles per ewe, 22 sheep; P less than 0.01), although the mean numbers of preovulatory-sized follicles (greater than or equal to 5 mm diam.) were similar (anoestrus, 1.3 +/- 0.2 per ewe; oestrous cycle, 1.0 +/- 0.1 per ewe). The ability of ovarian follicles to synthesize oestradiol did not differ between anoestrus and the breeding season as assessed from the levels of extant aromatase enzyme activity in granulosa cells and steroid concentrations in follicular fluid. Although the mean plasma concentration of LH did not differ between anoestrus and the luteal phase of the breeding season, the pattern of LH secretion differed markedly; on Day 9-10 of the oestrous cycle there were significantly more (P less than 0.001) high-amplitude LH peaks (i.e. greater than or equal to 1 ng/ml) in plasma and significantly fewer (P less than 0.001) low amplitude peaks (less than 1 ng/ml) than in anoestrous ewes. Moreover, the mean concentrations of FSH and prolactin were significantly lower during the luteal phase of the cycle than during anoestrus (FSH, P less than 0.05, prolactin, P less than 0.001). It is concluded that, in Romney ewes, the levels of antral follicular activity change throughout the year in synchrony with the circannual patterns of prolactin and day-length. Also, these data support the notion that anovulation during seasonal anoestrus is due to a reduced frequency of high-amplitude LH discharges from the pituitary gland.

Both TSH and gonadotropins stimulate the gonads in the perinatal period. Gonadotropins influence primarily the parenchyma and they induce an increase in the diameter of seminiferous tubules, and of the thickness of the ovarian cortex. TSH acts primarily on the interstice, but it acts also on the parenchyma and this action is more pronounced in the testis than in the ovary. The hormones can replace each other, and gonadotropins enhance the effect of TSH on the interstice.

The present study correlates ultrasound observations of ovaries with gonadotrophin and ovarian steroid levels in plasma in 18 women using oral contraception through 28 cycles. Follicles could often be made out with ultrasound. They were associated with measurable gonadotrophin values, but the resulting ovarian steroid production often seemed to be very low. However, there are exceptions as shown in one case described here in which ultrasound, gonadotrophin and oestrogen levels together show up coherently. Yet no ovulation was demonstrated. This preliminary study should encourage investigators to carry out further series.

In the present study, we have examined the role of gonadotropins and prostaglandins in the preovulatory increase of ovarian collagenase activity in the rat. Whole ovaries of immature PMSG-primed rats (20 IU) were removed before and 8 h after the rats were treated with human (h) CG, Nembutal, and/or indomethacin. The ovaries were homogenized in a solution containing Triton X-100 (0.25%) and centrifuged. Collagenase was extracted by resuspending the pellets in buffer containing 100 mM CaCl2, heating to 60 C for 6 min, and centrifuging. The supernatants were treated with dithiothreitol (2 mM) and iodoacetamide (5 mM) to inactivate collagenase inhibitors. Collagenase activity was measured as the percent digestion of 3H-type I collagen/100 microliters aliquot of ovarian sample. At zero time (52 h after PMSG), ovarian collagenase activity was 4.2 +/- 1.2% digestion (mean +/- SEM, n = 3). In ovaries collected 8 h after the endogenous LH surge or 8 h after the administration of 10 IU hCG at time zero, collagenase activity rose to 19.6 +/- 2.1 (n = 6) and 22.5 +/- 1.7% digestion (n = 11), respectively. Indomethacin (1.5 mg/100 g BW) administered 30 min after hCG, produced no change in collagenase activity (24.8 +/- 2.5% digestion, n = 7) although the expected increase in ovarian prostaglandin E after hCG treatment was blocked. When the endogenous LH surge was blocked with Nembutal (3 mg/100 g BW), collagenase activity in 8-h ovaries was 6.8 +/- 1.1% digestion (n = 10). The Nembutal block of the preovulatory collagenase increase was overcome by administration of hCG (8-h ovarian enzyme activity = 22.7 +/- 3.2% digestion, n = 8). These observations demonstrate that hCG stimulates ovarian collagenase activity and that this stimulation is not dependent on prostaglandin synthesis.

Female rats with showed 5-day ovarian cycles spontaneously, but 4-day cycles for periods of variable length after induction of pseudopregnancy, were examined. While the time of onset of the ovulatory LH surge at pro-oestrus was the same in both 4- and 5-day cycles, dioestrous progesterone concentrations were dissimilar. The most prominent feature was a sharp increase during the night of the first day of dioestrus of the 4-day cycle. The results are interpreted as suggesting that dioestrous steroid concentrations rather than pro-oestrous LH concentrations are important in establishing cycle duration.

Hypothalamic regulation of luteinizing hormone (LH) secretion and ovarian function were investigated in beef heifers by infusing LH-releasing hormone (LHRH) in a pulsatile manner (1 microgram/ml; 1 ml during 1 min every h) into the external jugular vein of 10 hypophysial stalk-transected (HST) animals. The heifers were HST approximately 30 mo earlier. All heifers had increased ovarian size during the LHRH infusion. The maximum ovarian size (16 +/- 2.7 cm3) was greater (P less than 0.01) than the initial ovarian size (8 +/- 1.4 cm3). Ovarian follicular growth occurred in 4 of 10 HST heifers in response to pulsatile LHRH infusion. In 2 heifers, an ovarian follicle developed to preovulatory size, but ovulation occurred in only 1 animal after the frequency of LHRH was increased (1 microgram every 20 min during 8 h). In blood samples obtained at 20-min intervals every 5th day, LH concentrations in peripheral serum remained consistently low (0.9 ng/ml) and nonepisodic in the 10 HST heifers during infusion of vehicle on the day before beginning LHRH. In 7 of 10 HST animals, episodic LH secretion occurred in response to pulsatile infusion of LHRH. In 3 of these long-term HST heifers, however, serum LH remained at basal levels and the isolated pituitary seemingly was unresponsive to pulsatile infusion of LHRH as indicated by sequential patterns of gonadotropin secretion obtained at 5-day intervals. These results indicate that pulsatile infusion of LHRH induces LH release in HST beef heifers.

The effects of age on the elevations of plasma luteinizing hormone (LH) after ovariectomy were studied in C57BL/6J mice. In longitudinal studies, mice ovariectomized at 4-6 months and sampled serially reached maximum plasma LH (200-300 ng/ml) after 1 month; these elevations were maintained to at least 15 months of age, when most intact mice have ceased cycling and have persistent vaginal cornification (PVC). In contrast, mice ovariectomized at 15 or 21 months had smaller LH elevations (to 150 ng/ml) 1 or 2 months after ovariectomy, as compared to younger (5- or 11-month-old) cycling mice whose LH was ca. 200 ng/ml 1 month after ovariectomy. The maintenance of LH elevations in chronically ovariectomized mice suggests that the smaller LH elevations in acutely ovariectomized mice of the same age may be an ovary-dependent aging phenomenon. Pilot studies detected no age effects on plasma LH turnover. Intact 20- to 26-month-old mice with leukocytic vaginal smears, low plasma estradiol (E2) and low progesterone had initially elevated plasma LH (ca. 125 ng/ml), if gross pathologic lesions were not present at necropsy. In contrast, old mice with cornified vaginal smears had higher plasma E2 and low (normal) plasma LH. The low plasma progesterone and elevated LH in older mice with leukocytic smears argues against a pseudopregnant status. Old mice of all vaginal smear types with pathologic lesions had low LH. Ovariectomy did not yield further increases of LH in old mice. The spontaneous elevation of plasma LH to ovariectomized levels in old intact mice with leukocytic vaginal smears and reduced plasma E2 implies that C57BL/6J mice eventually undergo ovarian changes analogous to menopause in humans.