The effect of prolactin and relaxin on insulin binding by adipocytes from pregnant women.

The effects of prolactin and relaxin on insulin binding by isolated human adipocytes from women at term gestation were studied in vitro. It was found that prolactin decreases, and relaxin increases, insulin binding to the adipocytes. Both changes appear to be due to alterations in the affinity of the insulin receptors. These effects seem to be mediated through specific prolactin and relaxin receptors of the adipocyte and require the presence of an intact cellular cytoskeleton. This suggests that one hormone, for example, prolactin, can interact with its own specific receptor and thereby after the affinity of a heterologous receptor for its hormone (insulin). Heterologous hormone-receptor complex interactions ("cross-talk") may be widespread and could represent a fundamental mechanism in the functioning of the endocrine system.