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• Expression of NPY in fish ovary is regulated by photoperiod and temperature. • Temperature regulates expression of ovarian NPY more effectively than photoperiod. • High temperature and long photoperiod also promote oogenesis and steroidogenesis. Authors have recently reported a gradual increase in neuropeptide Y expression in the ovarian follicles of Clarias batrachus with the progression of oogenesis, coinciding with increasing photoperiod and temperature. This indicates the involvement of photoperiod and temperature in controlling NPY expression. Therefore, a study was designed to investigate the role of photoperiod and temperature in regulation of NPY expression in ovarian follicles. The catfish were exposed to different photo-thermal regimes during the late-quiescence and late-recrudescence phases for one month, and the expression of NPY was analyzed along with other ovarian activities. Though the exposure of catfish to long photoperiod induced a marginal increase (1.5 fold) in NPY expression in follicular cells, the high temperature stimulated its expression more effectively (6–10 fold), irrespective of photoperiodic exposures. Exposure to long photoperiod and high temperature together induced NPY expression maximally in granulosa and thecal cells of fully grown oocytes, but exposure to low temperature decreased its expression significantly. The oogenic and steroidogenic activities were also promoted simultaneously after the exposure to high temperature and long photoperiod alone or in combination. However, the low temperature exposure suppressed the ovarian activities leading to atresia of advanced follicles. Thus it is suggested that photoperiod and temperature both affect NPY expression and ovarian recrudescence in fish but the influences of temperature seem to be more prominent. [ABSTRACT FROM AUTHOR]

The present study was undertaken to examine the cellular localization and potential steroidogenic role of neuropeptide Y (NPY) in the ovary of the freshwater catfish, Clarias batrachus . NPY-immunoreaction was observed in the follicular cells (granulosa and thecal cells) in the growing ovarian follicles, and the intensity of staining increased steadily from the initiation of follicular development until follicles were fully grown. Thereafter as follicles matured the stain intensity decreased. Positive correlations were found between NPY expression and the ovarian levels of 17β-estradiol, testosterone, and activities of 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β-HSD) in the ovary. In vitro NPY treatment stimulated the production of the two steroids and the activities of two enzymes. This is the first report of NPY immunoreactivity at the cellular level in the fish ovary and implicates this orexigenic peptide in the modulation of ovarian steroidogenesis. [ABSTRACT FROM AUTHOR]

In an earlier study we have demonstrated reproductive-stage dependent, cell specific existence of inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS)/NO system in testis of the catfish, Clarias batrachus . The present study is an extension to examine the role of NO in steroidogenesis and spermatogenesis through in vivo administration of a NO donor, sodium nitroprusside (SNP) and a NOS inhibitor, N-nitro- l -arginine methyl ester ( l -NAME) during the quiescence and recrudescence phase of the reproductive cycle of the catfish. Effects of these chemicals were assessed on the gonadosomatic index (GSI), levels of circulating & testicular testosterone, NO, activities of 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD) in testis, expression of different NOS isoforms and testicular morphology in relation to spermatogenesis. SNP treatment increased the GSI, testicular and circulating testosterone & NO, activities of testicular 3β-HSD & 17β-HSD, and expression of NOS isoforms. It also increased the area and perimeters of interstitium and seminiferous tubules in the testis. It accelerated the spermatogenesis, as was evident from the large number of spermatids/spermatozoa in seminiferous tubules and very few spermatogonial cells/primary spermatocytes in comparison to the control testis. On the contrary, l -NAME significantly suppressed GSI, testosterone & NO levels in serum and testis, and activities of testicular 3β-HSD & 17β-HSD. It also suppressed the expression of NOSs in testis. Though l -NAME did not alter the spermatogonial mitotic proliferation with the advancement of testicular recrudescence, it halted the progression of spermatogenesis (meiotic division and spermatozoa formation) as was clear from the increase in spermatogonial cells and very few advanced germ cells in the seminiferous tubules in l -NAME treated testis, compared to the control testis. The above noted effects were highly pronounced in the recrudescing catfish. Their effects were very marginal and at a particular dose levels of SNP and l -NAME in the quiescent testis. This study distinctly provides evidence of pro-steroidogenic and pro-spermatogenic role of NO. This study also demonstrates the existence of eNOS in fish testis for the first time. The positive feedback control of expression of all isoform of NOS in testis by NO is also noteworthy. [ABSTRACT FROM AUTHOR]

Nitric oxide, a gaseous molecule, is produced during the conversion of arginine to citrulline by the action of NOS isoforms (eNOS, iNOS or nNOS). Role of NO in regulation of mammalian reproduction is well established; however, practically no report is available on fishes. Hence, in the present study, expression of all three isoforms of NOS was worked out in the ovary of Clarias batrachus immunohistochemically during different phases of its reproductive cycle and its relation with ovarian activities. No immunoreactivity of eNOS was observed in the ovary of C. batrachus during the late-quiescence and early-recrudescence phases. While during the recrudescence phase (April and May) it expressed intensely in thecal and granulosa cells of the oocyte-II and III, but immune-intensity decreased in the late-recrudescence and spawning phases (June and July). Similar pattern of immunoprecipitation was also observed in case of iNOS. However, the immunoreactivity pattern of nNOS was quite varied, it expressed moderately only in the nucleus and cytoplasm of perinuclear and oocyte-I stages during late-quiescence phase. While during the early recrudescence phase, the expression of nNOS disappeared completely from the nucleus and cytoplasm, rather it expressed intensely in the thecal and granulosa cells, which declined in the late-recrudescence and spawning phases. Moderate immunoreactivity of iNOS could also be localized in the zona radiata of ovulated oocyte. The intense NOS immunoreactivity in the thecal and granulosa cells coincided with increased levels of ovarian NO and 17β-estradiol content. They exhibited statistically significant positive correlation amongst themselves, suggesting the involvement of ovarian NOS/NO system in oogenesis and steroidogenesis in the catfish. [ABSTRACT FROM AUTHOR]

Abstract: Many hormones are known for their role in the regulation of metabolic activities and somatic growth in fishes. The present study deals with the effects of malathion (an organophosphorous pesticide) on the levels of metabolic hormones that are responsible for promotion of somatic and ovarian growth of the freshwater catfish, Clarias batrachus. Malathion treatment for thirty days drastically reduced the food intake and body weight of fish. These fish also exhibited a great avoidance to food. Exposure of catfish to malathion reduced the levels of thyroxine (T4), triiodothyronine (T3), growth hormone (GH), insulin like growth factor-I (IGF-I), testosterone (T) and estradiol-17β (E2) in a dose dependent manner during all the studied reproductive phases, in general, except that malathion increased the level of GH during the quiescence phase. Significant reduction in muscle and hepatic protein content also occurred in the malathion-treated fish. Malathion exposure induced lipolysis too in the liver and muscle. The results thus support that malathion treatment disrupts the endocrine functions and the olfactory sensation responsible for food intake and gustatory feeding behavior, which ultimately leads to retardation of fish growth. [Copyright &y& Elsevier]

Abstract: The present in vitro study for the first time demonstrates the role of extragonadal hormones in regulation of NO production by testicular macrophages in vertebrates and paracrine role of NO in Leydig cell steroidogenesis in fishes. N-nitro L-arginine methyl ester (L-NAME - a NOS inhibitor) treatment substantially reduced NO production by testicular macrophages suggesting that testicular macrophages are one of the sources of testicular NO in the catfish, Clarias batrachus. Significant decline in NO production was also recorded following treatment of macrophages with the gonadotropin (GtH), growth hormone (GH) and insulin indicating that macrophage-produced NO is under endocrine inhibitory control. Treatment of Leydig cells with sodium nitroprusside (SNP) decreased testosterone (T) production. SNP treatment also remarkably suppressed the GtH, GH and insulin-stimulated T production by Leydig cells indicating that Leydig cell steroidogenesis is sensitive to exogenous NO. Further, effect of conditioned medium of testicular macrophages incubated with medium alone (non-treated TMCM) or GtH (GtH-treated TMCM) or GH (GH-treated TMCM) or insulin (insulin-treated TMCM) were also observed on Leydig cell T production. Non-treated TMCM as well as hormone-treated TMCM stimulated T production by Leydig cells; hormone-treated TMCM were more effective in stimulating T production than non-treated TMCM and/or hormones alone. These experiments altogether suggest that testicular macrophage secrete some factors, which influence Leydig cell steroidogenic activity through paracrine mechanism, and these paracrine secretions are under the endocrine control. Decline in NO in hormone-treated TMCM might also be one of the reasons for more stimulation in T production than that of hormones alone. [Copyright &y& Elsevier]

Abstract: Nitric oxide has been recognized as an important inter- and intra-cellular modulator of testicular steroidogenesis in higher vertebrates with conflicting results. Moreover, its role in regulation of testicular steroidogenesis in ectothermic vertebrates is non-existent. The present study was, therefore, undertaken to examine whether Leydig cells of a freshwater catfish, Clarias batrachus produce nitric oxide (NO), if so, does it regulate its steroidogenic activity? The purified Leydig cells were stained histochemically for NADPH-diaphorase (NADPH-d) activity, and immunocytochemically for neuronal and inducible nitric oxide synthase (nNOS and iNOS) like molecules. Leydig cells were also incubated with NOS inhibitor, N-nitro-l-arginine methyl ester (l-NAME), and NO donor, sodium nitroprusside (SNP). NO and testosterone released in incubation medium were analyzed. A distinct positive NAPDH-d staining was observed in Leydig cells. These cells also exhibited immunoprecipitation of variable intensity with nNOS and iNOS antibodies. Further, l-NAME treatment caused significant suppression in NO production and elevation in testosterone secretion by Leydig cells. On the contrary, exposure of Leydig cells to SNP resulted in increased NO production with concomitant decline in testosterone level. Thus, the present study reports NO production by Leydig cells in fish for the first time, which appears to inhibit its own androgen production. [Copyright &y& Elsevier]

Abstract: Although neuropeptide Y (NPY) has been known to influence the release of luteinizing hormone (LH) and growth hormone (GH) from the pituitary gland of teleosts, the NPY receptor subtypes involved in the regulatory processes have not been fully defined. An attempt has been made to study the involvement of NPY Y1 receptors, if any, in mediating the NPY-triggered stimulation of the LH and GH secreting cells in the pituitary of the catfish, Clarias batrachus. NPY (10ng/g of body wt) or NPY Y1 receptor agonist (Leu31-Pro34-NPY, 3ng/g of body wt) were administered by the intracranial route and the responses by the LH and GH cells in the pituitary were investigated with the help of immunocytochemistry. Both the agents caused a highly significant decrease (P <0.001) in the immunoreactivity of LH cells. However, the treatment with NPY Y1 receptor antagonist (BIBP 3226, 1ng/g of body wt), prior to NPY or NPY Y1 agonist, blocked the response by the LH cells; the profile of the cells was quite similar to that of the saline-injected control fish. GH cells also showed similar pattern of responses to these treatments. While NPY and NPY Y1 receptor agonist caused significant (P <0.001) decrease in the GH immunoreactivity, pretreatment with the NPY Y1 antagonist blocked the response. These results suggest that NPY may exercise a secretogogue-like action on the LH and GH cells in the pituitary of C. batrachus via NPY Y1 receptors. [Copyright &y& Elsevier]

Highlights: [•] Somatic as well as reproductive actions of GH is temperature dependent in the catfish, Clarias batrachus. [•] GH stimulates spermatogonial proliferation and accelerates spermatogenic processes. [•] GH promotes testosterone and estradiol production in the catfish. [•] Reproductive action of GH action is mediated through IGF-I in the catfish. [Copyright &y& Elsevier]