Steroids in the plasma of the winter flounder ( Pseudopleuronectes americanus walbaum). A seasonal study and investigation of steroid involvement in oocyte maturation

Abstract

Cortisol was a major steroid identified in the plasma of male and female Pseudopleuronectes americanus. Cortisone, corticosterone, 11-deoxycortisol, 11-deoxycorticosterone and 11-dehydrocorticosterone were identified at lower concentrations. In plasma from male fish testosterone concentrations changed only slightly during the annual cycle but 11-ketotestosterone concentrations rose dramatically near the time of spawning. Testosterone levels were highest prior to spawning in plasma from female fish but the concentrations of 11-ketotestosterone remained extremely low throughout the year. Progesterone, 17α- OH-progesterone and 20β-dihydro, 17α- OH-progesterone were also identified in plasma from female fish. Plasmas in which oocytes were stimulated to undergo meiotic maturation in vitro were found to contain greater concentrations of 17α-OH-Progesterone and 20β-dihydro, 17α- OH-progesterone than those which did not have this biological activity.