Estradiol-induced hepatic protein synthesis and transaminase activity in the male flounder, Platichthys flesus (L.).

A continued accumulation of vitellogenin was observed in the serum through 28 days after administration of spaced large doses of estradiol. The level of estradiol in the serum reached a maximum on Day 4, followed by a continued decrease until a basal concentration was reached at Day 15. The estradiol treatment increased the in vitro hepatic protein synthesis activity, measured as polyphenylalanine synthesis per unit cytoplasmic RNA, within 2-4 days reaching a maximum after 7 days. The effect was transitory and reduced to less than 50% within 15 days. After restimulation a second rise in protein synthesis activity was observed. The cellular content of bulk RNA i the liver showed a slow but steady accumulation through the 28 days. The specific activity of glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase in the liver decreased 35 and 20% relative to control, respectively, within 7 days after the first stimulation and again 14 days after restimulation. The concentration of serum protein showed a steady increase throughout the experimental period. The concentration of serum ninhydrine positive substances was lowered to 50% relative to the controls within the first 7 days after start of treatment with hormone.