An inverse relationship between receptor internalization and the fraction of laterally mobile receptors for the vasopressin renal‐type V2‐receptor

Abstract
Lateral mobility of the vasopressin renal‐type V2‐receptor was investigated in LLC‐PK1, porcine epithelial cells using the technique of fluorescence microphotolysis (photobleaching) and a rhodamine‐labelled vasopressin analogue. At various times after ligand addition, cells were analyzed for both receptor lateral mobility and ligand internalization. The V2‐receptor mobile fraction diminished from 0.9 to 0.43 over 60 min at 37°C. whereas the apparent lateral diffusion coefficient remained essentially unchanged (2–3 × 10−10cm2s). Interestingly, the fraction of immobile V2‐receptors corresponded exactly with the fraction of internalized receptors, implying a functional relationship. These observations together with comparable results reported for other polypeptide hormone receptors indicate a possible machanistic role for receptor immobilization in the desensitization of hormonal response.