Article ID Journal Published Year Pages File Type
5587839 General and Comparative Endocrinology 2016 8 Pages PDF
Abstract
Photoperiodic regulation of testicular steroidogenesis through modulation of MT1R expression and local melatonin content is well established. However, additional mediators besides local melatonergic system in photoperiodic control of testicular steroidogenesis in golden hamster have not been studied in detail. Endogenous opioid peptides (EOP) are known to regulate reproduction via acting at multiple levels of the hypothalamus-pituitary-gonadal (HPG) axis. The presence of β-endorphin, a naturally occurring opioid peptide, and its receptor (μ-opioid receptor, μOR) has been reported in rat testes; however the functional significance of photoperiodic regulation μOR in testicular steroidogenesis is not clear. In the present study, we assessed the effect of Naltrexone (Nal), a μOR antagonist, in photoperiodic regulation of testicular steroidogenesis. Immunohistochemical (IHC) localization and expression of μOR along with the expression of steroidogenic markers in testes was analyzed through western blot analyses. IHC suggest immunoreactivity for μOR in Leydig cells with strong immunoreactivity under SD (short-day) condition, whereas weak immunoreactivity was observed under LD (long-day). The expression of μOR was significantly decreased following Nal administration in both the photoperiodic conditions. The localization and differential photoperiodic regulation of μOR in Leydig cells suggests its involvement in testicular steroidogenesis. Further, Nal administration significantly increased the expression of steroidogenic markers (AR, StAR, P450SCC, LH-R, 3β-HSD and 17-HSD) and plasma testosterone concentration under SD condition as compared to SD-control. We may therefore suggest that photoperiod differentially regulates the expression of μOR which thereby mediates the inhibitory effect of melatonin on testicular steroidogenesis.
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Life Sciences Biochemistry, Genetics and Molecular Biology Endocrinology
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