EVIDENCE FOR NONSTEROIDAL GONADAL REGULATOR(S) OF GONADOTROPIN-RELEASE IN THE GOLDFISH, CARASSIUS-AURATUS

In mammals, it is well documented that in addition to steroidal hormon es, gonads also produce a variety of non-steroidal proteins and peptid es that can feed back to regulate pituitary gonadotropin secretion. Th e best studied among these non-steroidal substances are inhibin and ac tivin. The present study demonstrates that in sharp contrast to mammal ian gonadal extracts which usually have inhibitory effects on mammalia n gonadotropin secretion due to inhibin, the aqueous goldfish gonadal extracts stimulate pituitary gonadotropin-II (GTH-II) release in goldf ish. Interestingly, the actions of the goldfish gonadal extracts are s imilar to our previously reported effects of porcine follicular fluid on goldfish GTH-II release. The stimulatory activities of goldfish ova rian extracts and the pituitary responsiveness to this stimulation flu ctuate dramatically with the ovarian development. The results presente d in this paper support our previous findings that porcine inhibin and activin stimulate goldfish gonadotropin release and the immunoreactiv e inhibin and activin subunits are present in the goldfish gonads.