Different regulation of insulin receptors in intracellular (Golgi) and plasma membranes from livers of obese and lean mice.

Insulin binding to Golgi and plasmalemma fractions from the liver of obese (ob/bo and db/db) and lean control mice was studied. The specficiity of binding in Golgi fractions (Golgi vesicles and Golgi cisternae) was identical to that observed previously in rat liver Golgi fractions and plasmalemma. Binding to plasmalemma was much lower in obese compared to lean mice, but binding to Golgi cisternae was either not changed (ob/ob) or slightly increased (db/db) in obese compared to lean littermates. These observations suggest that intracellular (Golgi cisternae) insulin receptors are regulated differently from those of the plasmalemma. We propose that insulin affects hepatic receptor content in two different ways. On the one hand plasmalemma receptor loss is accelerated, and on the other hand intracellular receptor production is increased. This model can explain in one framework the effect on insulin in reducing and prolactin in augmenting the level of their respective hepatic receptors.