ISOLATION, PARTIAL CHARACTERIZATION, INDUCTION, AND THE OCCURRENCE INPLASMA OF THE MAJOR VITELLINE ENVELOPE PROTEINS IN THE ATLANTIC HALIBUT (HIPPOGLOSSUS-HIPPOGLOSSUS) DURING SEXUAL-MATURATION

The vitelline envelope of Atlantic halibut (Hippoglossus hippoglossus) is composed mainly of two major and two minor proteins. Estradiol-17 beta induces the two major vitelline envelope proteins in halibut of b oth sexes. These proteins were also found in plasma of vitellogenic fe males. The origin of the two major vitelline envelope proteins is not restricted to the ovary, as male halibut synthesize these proteins aft er treatment with estradiol-17 beta. Individual female halibut were fo llowed and plasma sampled from May to March. Plasma levels of estradio l-17 beta increased in October, peaked in early February, and declined until the last ovulation in March. In October, the two major vitellin e envelope proteins were first detected in plasma and the amount remai ned elevated until early March. Prior to the last ovulation, the amoun t decreased. Plasma vitellogenin varied in a similar way. The results provide strong evidence that the physiological regulation of the synth esis of the major vitelline envelope proteins in teleosts is controlle d by the female sex steroid estradiol-17 beta.