Semicarbazide disturbs the reproductive system of male zebrafish (Danio rerio) through the GABAergic system

•Male zebrafish were exposed to semicarbazide for 28 d.•Testis histology was affected after semicarbazide exposure.•Semicarbazide exposure reduced plasma testosterone and 17β-estradiol levels.•Semicarbazide exposure altered gene transcription along the GABAergic system.•Semicarbazide disturbs the reproductive system of male zebrafish.

Semicarbazide (SMC), an emerging water contaminant, exerts anti-estrogenic effects in female zebrafish. However, the exact influence of SMC on male reproduction remains unclear. In this study, adult male zebrafish were exposed to 1-1000 μg/L SMC in a semi-static system for 28 d prior to examining the testicular somatic index (TSI), testis histology, plasma sex hormone levels, and the transcription of genes involved in reproduction. The results showed that testicular morphology was altered and TSI was down-regulated by high concentrations of SMC (≥100 μg/L and 1000 μg/L, respectively). Plasma testosterone and 17β-estradiol concentrations were significantly decreased by all of the SMC treatments, along with down-regulation of the corresponding steroidogenic gene transcripts. These changes were associated with the inhibition of gamma-aminobutyric acid synthesis and function, in addition to the decreased expression of reproductive regulators. Our results contribute to elucidating the mechanisms underlying the adverse reproductive effects of SMC in male zebrafish.

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