Levels of 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one, 3 beta,17 alpha,20 alpha-trihydroxy-5 beta-pregnane, and other sex steroids, in blood plasma of male dab, Limanda limanda (marine flatfish) injected with human chorionic gonadotrophin.

In a previous study, plasma sex steroid levels were measured in female dab (Limanda limanda) induced to ovulate by injections of human chorionic gonadotrophin (HCG). In the present study, a similar experiment was carried out on male dabs. In common with female dabs, 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one and 3 beta,17 alpha,20 alpha-trihydroxy-5 beta-pregnane showed the greatest response. Their plasma levels increased, respectively, from 6 +/- 1.6 and 13 +/- 6.2 ng/ml to ca. 62 ng/ml within 36 hr and then decreased. Levels of both steroids remained low in fish injected with saline. There was no statistically significant effect of HCG on plasma testosterone or 11-ketotestosterone concentrations. Initial levels of both hormones were between 10 and 20 ng/ml, and decreased simultaneously in both HCG- and saline-injected fish. Levels of 17 alpha-hydroxy-4-pregnen-3,20-dione, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one, 11-deoxycortisol, and 17 alpha,20 beta, 21-trihydroxy-4-pregnen-3-one were mostly below the detection limits of the assays (0.4 ng/ml). There was no statistically significant effect of HCG on either the total volume of milt collected or the proportion occupied by spermatozoa.