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Advantage was taken of a specific and sensitive bioassay for rat plasma adrenocorticotropin (ACTH) based on the dispersion of rat adrenal cells with trysin, to investigate the relationship between plasma corticosterone concentration and inhibition of ACTH release under steady-state conditions achieved by graded rates (0-5.12 mug/min per 100 g body weight) of intravenous infusion of the steroid for 45 min in 28-day adrenalectomized rats. In contrast to prior reports involving suppression of stress-induced ACTH release, the inhibitory effect of corticosterone was shown, under our experimental conditions, to be exerted also on the basal rate of ACTH secretion. Indeed, a slight though not significant decrease of plasma ACTH concentration was observed with the corticosterone infusion rate of 0.64 mg/min per 100 g body weight, and further progressive and highly significant drops in concentration were recorded for infusion rates of 2.56 and 5.12 mg/min per 100 g body weight. An increase of the metabolic clearance rate of corticosterone, observed as a function of the infusion rate, was ascribed to saturation by the steroid of the plasma transcortin binding sites.

The effect of corticosterone administered in different doses has been studied on hypothalamic serotonin (5-HT) content. A single intraperitoneal injection of the hormone in doses of 1.0 and 2.0 mg/kg bw. increased the serotonin content of the hypothalamus at 30 min after administration. Five mg/kg had no effect, while 10.0 mg/kg decreased the serotonin content. The data provide an explanation for the controversial findings of different authors having used different doses of different glucocorticoids and on the basis of the results it is emphasized that the action of glucocorticoids on hypothalamic 5-HT content is a dose-dependent dual effect.

Central and peripheral humoral responses of the adrenocortical system were measured for 2 h after the application of several stimuli. Two min after the onset of the stresses of sham-adrenalectomy or laparotomy with intestinal traction there was a 4-6 fold increase in hypothalamic CRF content as compared to control content, This is the usual CRF response to stress. In contrast, after adrenalectomy or manipulation of the pedicles of adrenal glands; CRF content at 2 min was only slightly increased above baseline values. This finding suggests that touching the adrenal vascular and nervous supply results in a direct neural input to the hypothalamus that is qualitatively different from most other stimuli. At times later than 2 min after stress, whem plasma corticosterone levels rise in the intact rat, the patterns of CRF and ACTH responses that were observed after adrenalectomy were determined by whether corticosterone replacement therapy was given. Without corticosterone replacement, the CRF and ACTH responses to adrenalectomy resembled those of laparotomy with intestinal traction. When corticosterone was administered 2 and 40 min after adrenalectomy, the CRF and ACTH responses resembled those of sham-adrenalectomy. At 20 min, CRF content was low after laparotomy with intestinal traction or adrenalectomy and high after shan-adrenalectomy or adrenalectomy with corticosterone replacement. Plasma ACTH peaked by 20 min, and remained high for 2 h after the first 2 stimuli, and was significantly decreased from the 20 min peak by 40 min after application of the latter stimuli. CRF content increased to a second peak 80 min after laparotomy with intestinal traction or adrenalectomy. This rise in CRF must represent increased formation of the releasing factor because ACTH levels were elevated and constant for the preceding 60 min. After sham-adrenalectomy or adrenalectomy with corticosterone replacement, CRF content and ACTH are low at 80 min. Measurement of circulating ACTH levels in conjunction with CRF content after these stimuli have yielded sufficient information to assign mechanisms of altered synthesis and secretion to explain the observed changes in CRF content. Corticosterone damps the adrenocortical system response to the stimuli of sham-adrenalectomy or adrenalectomy with corticosterone replacement by two mechanisms. Firstly, it acts to inhibit CRF secretion probably via rate-sensitive feedback. Secondly, it acts to inhibit the second wave of CRF formation that is observed 80 min after stress is applied, probably via the proportional feedback mechanism.

1 Administration of corticosterone caused a 47% reduction in the cholinesterase (ChE) activity of homogenates of the rat anococcygeus muscle. 2 ChE activity was also reduced by morphine withdrawal and this effect was abolished by the corticosteroid synthesis inhibitor, metyrapone. 3 A single dose of reserpine reduced ChE activity in normal but not in adrenalectomized rats. 4 ChE activity was increased by adrenalectomy or by metyrapone treatment. 5 The mechanism of the corticosteroid-induced reduction in ChE activity is discussed. 6 The reduction in ChE activity produced by corticosterone, morphine withdrawal, or a single dose of reserpine might explain the leftward shift of the dose-% response curve to acetylcholine produced by these procedures in the isolated anococcygeus muscle of the rat.

Pituitary and plasma ACTH and plasma corticosterone were measured at various times after adrenal enucleation or adrenalectomy. The changes in ACTH could be inversely correlated with those in plasma corticosterone. They could also be prevented by maintenance therapy with the steroid. The results indicate that the corticosteroids control both the release and the synthesis of ACTH but that their effect is predominantly on the release of the hormone.

The effects of glucocorticoid hormone on the metabolism of brain 5-hydroxytryptamine (5-HT) were studied in mice. A single injection of hydrocortisone acetate (HCA; 20 mg/kg, i.p.) accelerated the accumulation of 5-HT in whole brain after inhibition of monoamine oxidase activity by paragyline. The hormone did not appear to change brain tryptophan hydroxylase or 5-hydroxytryptophan decarboxylase activity. However, tryptophan levels in brain were elevated by 50% within 1 h after treatment with HCA. The effect of HCA on brain tryptophan levels was localized mainly in the nerve endings. In vitro synaptosomal preparations, HCA at 10(-5)-10(-7)M or corticosterone at 10(-5) M was found to stimulate the uptake of L-[3H]-tryptophan by the synaptosomes while androgenic and progesterone-like steroids were ineffective. These results demonstrate that glucocorticoids may directly act on nerve terminals in the regulation of 5-HT synthesis through an action on the uptake of tryptophan.

Intestinal absorption of fluid and NaCl in rats is significantly decreased after hypophysectomy and increased in rats with pituitary implants. Oestrogen and reserpine significantly stimulate mucosal fluid and NaCl transfer in both normal and adrenalectomized rats, comparable to the effects of administration of prolactin. In intact rats, ergocryptine enhanced intestinal absorption of fluid and NaCl; however, it failed to exert any effects in adrenalectomized rats. Adrenalectomy alone had no adverse effects on intestinal absorption in saline-compensated rats. The administration of corticosterone alone or together with prolactin significantly enhanced intestinal absorption, although the effect of corticosterone alone was more variable. These data strongly suggest that increased endogenous prolactin levels produce stimulatory effects on intestinal absorption of fluid and NaCl by the rat jejunum.

In order to characterize the uterine progesterone-binding proteins of oestrogen-primed and unprimed, ovariectomized immature and adult golden hamsters, cytosols were incubated with [3H]progesterone and/or other steroids and analyzed by sucrose-glycerol density gradient ultracentrifugation. Progesterone-binding components with sedimentation coefficients of 7S and 4.5S were found in the uterine cytosols, but not in the cytosols from the hypothalamus, pituitary, diaphragm, or small intestine. Oestradiol-17beta markedly elevated the level of 7S uterine receptor and this increase appeared to be due to new receptor synthesis, since actinomycin D and cycloheximide blocked this response. Fifty to 100 mug of oestradiol-17beta per kg body weight was found to promote a maximum increase in the 7S macromolecular component. The 7S receptor showed a tendency to saturate at 1 X 10(-7) M [1,2-3H]progesterone, indicating limited capacity. At a molar ratio of 100:1, unlabeled progesterone competed effectively for 7S and 4,5S [3H]progesterone binding, whereas 5alpha-pregnane-3,20-dione, oestradiol-17beta and testosterone did not. Moreover, [1,2-3H]cortisol and [1,2-3H]corticosterone did not bind to the 7S receptor, implying steroid specificity. CI-628, a non-steroid oestrogen antagonist, completely prevented [6,7-3H]oestradiol-17beta binding to its 8.5S uterine cytosol receptor, but was entirely without effect on 7S and 4.5S [3H]progesterone binding. Pronase, but not DNase or RNase, abolished 7S and 4.5S progesterone binding, suggesting that the binders are at least in part protein. Protamine sulphate and p-hydroxymercuribenzoate also obliterated 7S binding, implying that this receptor may be an acidic protein which contains sulfhydryl groups that are necessary for progesterone binding.

The mouse cervical cell response to progesterone, corticosterone, and androgens was studied in vitro and comparatively by grafts on males. Contrary to the exocervical cells which responded more or less to the three steroid hormones, the endocervical cells responded exclusively to progesterone even in an estrogen free system. This result suggests the existence in the mouse endocervical cells of specific receptors to progesterone and indicates that the squamons cells of the uterine cervix have a different response to steroid hormones depending on where these cells are located.

The tricyclic antidepressant drugs: imipramine, opipramol, amitryptiline and nortryptiline inhibit development of experimental arterial hypertension in rats.

The messenger RNA rat alpha2u globulin has been identified and quantitated in a cell-free translational system derived from Krebs II ascites cells. Hepatic tissue of the mature male rats which normally produce alpha2u globulin was also found to contain a high level of alpha2u mRNA. Approximately 1.6 per cent of all poly(A) containing RNA of the adult male rat liver could be accounted for alpha2u messenger activity. Female rats do not produce alpha2u globulin and no alpha2u mRNA activity could be detected in the poly(A) containing RNA fraction obtained from the livers of these animals. However, androgen treatment to spayed female rats was found to induce the parallel appearance to both alpha2u globulin and its corresponding mRNA. Both hypophysectomy and adrenalectomy which are known to reduce the level of alpha2u globulin in the urine of male rats were found also to reduce the hepatic level of alpha2u mRNA. The results indicate that hormonal control of alpha2u globulin synthesis in rat liver is achieved primarily through regulation of its translatable mRNA level and that more than one hormone may participate in this regulation.

Pieces of skin from 13-5- to 15-day-old foetal mice were grown in organ culture in a biological medium with or without the addition of hormonal steroidsmcortisol (7-5 mug/ml) caused thinning of the non-cornified epidermis and flattening of the stratum granulosum after 3 days. By 6 days the epidermis was thinner and hair follicles were regressing, and these changes continued up to 12 days. Administration of corticosterone (5 mug/ml) also produced thinning of the epidermis and regression of the follicles after 6 days. Good differentiation of epidermis and hair follicles was obtained when testosterone (100 mug/ml) was added to the medium. The non-cornified epidermal layers were similar to those of control cultures at 3 days but less than half as thick at 6 days. Hair follicles differentiated as rapidly in medium containing testosterone as in normal medium, but, unlike in the latter medium, also developed sebaceous gland anlagen at 6 days. Some explants in testosterone medium showed signs of sebaceous cell differentiation at 9 days.

In sheep with both adrenals removed and one re-implanted in the neck, functional adrenalectomy was produced in conscious undisturbed animals by occluding the blood supply to the transplanted gland. Functional adrenalectomy caused a fall in potassium excretion and a very large increase in sodium excretion and was reversed by aldosterone. Hydrocortisone infusions slightly increased potassium excretion and reduced solute-free water reabsorption. Preliminary evidence suggests that potassium secretion into urine was still occurring during the 8 hr period of adrenal occlusion and functional adrenalectomy.

The functional zonation in the adrenocortical tissue of the duck was experimentally investigated after chronic administration of corticosteroids of different types (corticosterone, desoxycorticosterone, dexamethasone) and salt loading (chlorides of sodium and potassium). The cytomorphology of the interrenal cells belonging to subcapsular and central zones was explored by light- and electron microscopy and by biochemical analysis of plasma corticosterone. Corticoid-induced involution of the interrenal tissue, or hyperactivity elicited by salt loading were evident in both subcapsular and central regions of the gland. In the duck the adrenocortical tissue appears to be devoid of steroidogenic functional differentiation. The modifications of different cellular organelles and inclusions can be explained in the light of known concepts about corticosteroid metabolism. The depression of plasma corticosterone titre in corticosteroid-treated animals agrees with the image of cytological inhibition. The lowered corticosterone value in KCl-loaded ducks signifies increased peripheral metabolism of this hormone. The hypercorticosteronemia in NaCl-loaded ducks is probably related to activation of the nasal gland under osmotic stress.

The effects of cortisol, estradiol, and testosterone on somatomedin action on cartilage incubated in vitro have been examined. The addition of hormones in the absence of serum had no effect on the incorporation of sulfate by cartilage from hypophysectomized rats, embryonic chicks, or normal young pigs. Normal human serum provided a source of somatomedin which stimulated the incorporation of sulfate by cartilage in a dose-response relationship; the potency of serum with and without added steroid hormone was determined after formal parallel-line analysis. Moderately supraphysiologic levels of cortisol, 17 beta-estradiol, and testosterone generally had little effect on somatomedin action in the test systems. Very high levels of serum cortisol (100-1000 mug/100 ml) inhibited somatomedin action on pig cartilage, but had little effect on rat or chick cartilage. A 20 ng/100 ml increase in serum estradiol had no effect on somatomedin action on chick cartilage, but appeared to enhance somatomedin action on pig cartilage. A 5 mug/100 ml increase in serum testosterone did not affect somatomedin action on either chick or pig cartilage. These studies suggest that the alteration of somatomedin action is not a major mechanism in the effect of steroid hormones on growth. In addition, since modest increases in serum levels of cortisol, estradiol, and testosterone had little effect on somatomedin action in our assay systems, these systems should be satisfactory for the study of hormone effects on somatomedin generation.

ACTH administration (80 IU/day for 5 days), which produces hypertension and charateristic metabolic effects in sheep (38), has been compared with the effect of intravenous infusion of cortisol (5 mg/h), corticosterone (0.5 mg/h), deoxycorticosterone (50 mug/h), and 11-deoxycortisol (1 mg/h), each given singly for 5 days. Further, a mixture consisting of aldosterone (3 mug/h), cortisol (5 mg/h), deoxycorticosterone (25 mug/h), corticosterone (0.5 mg/h), and 11-deoxycortisol (1 mg/h), was also infused intravenously for 5 days. In another series of experiments, 18-hydroxydeoxycorticosterone (100 mg/h) was also included in the combined-steroid solution. With the exception of 18-hydroxydeoxycorticosterone, which was not measured, the rates of infusionproduced peripheral arterial blood levels of the steroids similiar to those seen with ACTH stimulation. Blood pressure,water intake, urine output, and plasma and urinary electrolytes were measured: individual steroids had little effect on these, but manyof the metabolic changes produced by ATCH (hypokalemia and increased water intake andurine output) were produced by the combined-steroid infusion. However, the combined-steroid infusion failed to induce an increase in blood pressure similiar to that seen inthe ACTH experiments. Thus the findings are against a major role in ACTH hypertension for any steroid used, either singly or in combination. As yet unrecgnized factor/s may be involved in the ACTH-induced hypertension.