IGF-I receptor binding, autophosphorylation, and kinase activity in kidney and muscle of acutely uremic rats

Following acute tubular necrosis (ATN), kidney plasma membrane insulin-like growth factor-I (IGF-I) receptor number increases markedly, although IGF-I receptor mRNA levels do not change. To determine whether this increase could represent a redistribution of intracellular receptors and whether receptor function is intact in acute uremia, rats with ATN of 2 days duration and pair-fed controls were studied. Skeletal muscle receptor binding was unchanged. In contrast, binding to receptors in solubilized cortex and isolated cortical plasma membranes increased significantly due to an increase in receptor number. However, the increase in membrane binding was threefold greater than the increase in solubilized cortex binding. This indicates that the increase in total cellular IGF-I receptors can only account for a minor portion of the increase in abundance of plasma membrane receptors number and is consistent with a redistribution of receptors from an intracellular to a membrane location as the major mechanism. Au...