[Study of insulin-receptor interactions in plasma membrane of rat liver using antibodies against insulin]

Abstract

Preincubation of rat liver cell plasma membranes with antiinsulin serum (AIS) results in a 3-fold increase of specific binding of [125I]insulin added to AIS-free membranes. The degree of such increase depends on preincubation time and AIS concentration; at a rise of both parameters the dependence curve shown a plateau. The Scatchard plots suggest that preincubation with AIS increases the high and low affinity of binding sites; their number remains thereby unchanged. Using several types of immune and non-immune sera for preincubation the specificity of this effect was established. It was assumed that the antibodies initiate the immunological reaction of the membrane. Study of AIS effect on dissociation of membrane-bound labelled insulins differing in their affinities for the given AIS revealed that the antibodies can interact with the newly formed hormone-receptor complex but cannot affect the receptor within insulin. It is concluded that the intact hepatocyte membrane contains a receptor-bound insulin which is a target of AIS action. The antigen-antibody interaction changes the functional state of occupied and free receptors which bind [125I]insulin. The latter becomes repeatedly involved in this process as a result of destabilization of site-site interactions provoked by antibodies against the hormones.