Receptors for Insulin and Insulin-Like Growth Factors I and II in PCD Mice and Diabetic Rats are Unaltered: An Autoradiographic Study

Abstract

Specific receptors for insulin and the insulin-like growth factors, IGF-I and IGF-II, are present in the central nervous system. Insulin binding sites were initially identified and localized to discrete areas of rat brain using membrane preparations (Havrankova et al., 1978) with the highest concentration in the olfactory bulb, limbic system and hypothalamus. Later studies, which combined autoradiography and radioreceptors assays using fresh frozen rat tissue slices (Hill et al, 1986), showed that specific binding of insulin is distributed throughout the brain in well defined neuroanatomic areas, and confirmed the earlier study by showing greatest density in the olfactory bulb and limbic system. Specific binding was demonstrated with competition studies which were like those of typical insulin receptors. We have also used autoradiography to study the binding sites of [¹²⁵-I] IGF-I and [¹²⁵I] IGF-II in rat brain and compared the pattern of binding to that of insulin (Lesniak et al, 1988).