Polypeptide hormone binding sites in vivo: initial localization of 125I-labeled insulin to hepatocyte plasmalemma as visualized by electron microscope radioautography

The rationale of the specific-binding assay was applied to the detection of the liver insulin receptor in vivo. Quantitative electron microscope radioautography indicated that, 3 min after an intraportal injection, 125I-insulin was exclusively located to the hepatocyte plasmalemma.