Effects of hCG and of season on in vitro steroidogenesis by 18 - day chick embryo

Fragmented 18-day chick embryo gonads were explanted on synthetic media in the presence of hCG added to 24 h cultures at the beginning (0 h) and to 48 h cultures, only after 24 h or at 0 and 24 h. The production of seven steroids was assayed by RIA and compared to that of control cultures containing no hCG. The levels were expressed as in vitro production per gonad (after deduction of the non-explanted gonadal content). When 5 IU of hCG were added to the 24 h culture media at 0 h, the overall steroidogenesis of the left and right gonads of both sexes increased significantly, the DHA in both sexes showing the most increment while A’-steroid (Prog. and A4-dione) production was not stimulated. Moreover, female gonad DHA production, as in the controls, was always higher than that of the testis. The female gonads produced mainly more E2, while testis T production was stimulated. Nevertheless, the discrepancy (observed earlier in the controls) between T and E2 balances of the left and right female gonads, and of the female and male gonads, was maintained under stimulation with female gonads and even increased with testis. A higher dose of hCG (15 IU), in these conditions, did not however further stimulate