In vivo demonstration by radioautography of binding sites for insulin in liver, kidney, and calcified tissues of the rat.

Abstract

An in vivo binding assay using radioautography was employed to visualize insulin receptors in rat tissues. Two and one-half minutes after the intravenous injection of 125I-insulin, free hormone was separated from bound hormone by whole body perfusion with lactated Ringer's solution followed by perfusion with glutaraldehyde. The localization of bound hormone, fixed in situ by perfusion with glutaraldehyde, was determined. Nonspecific binding of labeled insulin was noted in the proximal convoluted tubules of the kidney cortex, prebone and adjacent bone, predentin and adjacent dentin, and enamel. Specific binding sites were observed at the periphery of hepatocytes, over osteoblasts, and in relation to the endothelial cells of fenestrated capillaries within the papillary layer of the maturation zone of the incisors.