Hormonal influences on the middle-affinity estrogen-binding sites in the liver of the newt Pleurodeles waltl

Abstract

The effects of hormonal changes on the male-specific, middle-affinity, estrogen-binding component (MEBC) were investigated in the Pleurodele. Induction of MEBC was shown to be under androgen control, similar to that observed for the cytoplasmic middle-affinity estrogen-binding sites in rat liver and human hepatoma cells. But, in contrast to the malespecific middle-affinity estrogen-binding sites identified in the rat, the administration of estrogen to male Pleurodeles did not lead to the disappearance of MEBC but raised levels significantly. The MEBC displays the properties of type II middle-affinity estrogen-binding sites, which are characterized by an oestrogen-dependent rise, a sensitivity to reducing agents, a specificity for diethylstilbestrol, and a binding capacity enhanced by increasing dilutions of cytosol. In female Pleurodeles, MEBC can be induced by treatment with androgens. This induction appears to be modulated by the estrogen/androgen ratio. The induction of MEBC and the estrogen-dependent increase in the male were not found to be correlated with hepatocyte proliferation.