Reproductive status dependent efficacy of exogenous melatonin in ameliorating bisphenol-A (BPA) induced testicular impairments in an annual gonadal cycle of Clarias batrachus.

Pineal hormone melatonin coordinates the rhythmicity of reproductive events and ensuring the time specific germ cells maturation in seasonally breeding fish. Gonadal functions are desynchronized by various environmental pollutants which act as 'endocrine disrupting chemicals' (EDC). Present study provides comprehensive evidences for reproductive status-specific potent role of melatonin against a widely distributed EDC, bisphenol-A (BPA), induced cellular stress in the testes of Catfish, Clarias batrachus. Adult male fish were exposed to BPA and melatonin, either alone, or in combination, or with luzindole (melatonin receptor antagonist), for 30 days throughout the annual gonadal cycle. We evaluated melatonin concentrations, germ cell kinetics, meiotic progression, status of stress, apoptosis, and steroidogenic functions in testis. Using ordination analyses, we determined the differential effects of treatment regimens and reproductive phase transitions on the studied variables. BPA exposure significantly modulated gonadosomatic index (GSI), seminiferous tubules architecture and haploid cell populations depending upon the reproductive status. Intra-testicular stress status, cell death were markedly elevated following BPA exposure along with the suppression of enzymatic (SOD, CAT, GPx) and non-enzymatic (GSH) antioxidants. Melatonin co-administration with BPA regulated GSI and germ cell maturation as well as effectively restored testicular activity by enhancing antioxidative parameters and suppressing apoptosis possibly through receptor, MT1R, as it was evidenced by luzindole treatment. BPA also deregulated phase-specific expression of steroidogenic genes (StAR, 3β-hsd and 17β-hsd), involved in spermatogenesis. Collectively, present findings demonstrate the efficacy of melatonin to alleviate BPA-induced impairments of testicular functions may be through its receptor for the first time in any non-mammalian species.