Abstract
Adult male and female air-breathing catfish Clarias gariepinus were treated with ethynylestradiol (EE 2) and methyltestosterone (MT) at concentrations of 1 μg/L, respectively for 21 days. EE 2 treatment caused disappearance of spermatids/sperm from several testicular lumen/lobules in males while MT treatment to females led to precocious ovarian development. EE 2 caused significant fluid retention in all tissues including peritoneal cavity and seminal vesicles. Immunocytochemical localization of catfish GnRH (cfGnRH) and luteinizing hormone (LH) in preoptic area-hypothalamus (POA-H) and pituitary, respectively, revealed decreased immunoreactivity (ir-) following EE 2 treatment in males. MT treatment however caused no observable change in cfGnRH ir- and a significant increase in LH ir- in females. Semi-quantitative RT-PCR analysis indicated that cfGnRH transcripts in POA-H decreased significantly following EE 2 and MT treatment in males and females, respectively. Levels of POA-H dopamine (inhibitory monoamine for gonadotropin [GTH] synthesis and release) increased following EE 2 and MT treatment in males and females while levels of serotonin and norepinephrine (GTH-stimulatory monoamines) decreased significantly. The results demonstrate a direct in vivo effect of sex steroid analogs on cfGnRH–LH axis and monoaminergic system vis-à-vis on gonads in addition to probable direct action on gonads.
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