Epidermal growth factor binding to cortical basolateral membranes in compensatory renal hypertrophy

We studied epidermal growth factor (EGF) binding to renal basolateral membranes before and following unilateral nephrectomy. After 48 h unilateral nephrectomy there was a small increase in kidney cortex weight but EGF binding was unchanged, suggesting that alterations in EGF binding do not play a role in early renal hypertrophy. In contrast, 3 week unilateral nephrectomy was associated with a significant decrease in the Bmax of the high affinity binding sites for EGF without a change in the affinity constant. The changes in EGF binding seemed specific since binding for insulin was not changed by 3 week unilateral nephrectomy. The changes in EGF binding were not correlated with changes in Na-H antiporter activity elicited by unilateral nephrectomy but seemed inversely correlated with changes in renal cortical weight. Our results demonstrate that unilateral nephrectomy is not associated with changes in EGF binding in early stages, but is associated with a decrease in the number of high affinity binding sites after 3 weeks. This suggests that in the steady state, compensatory renal hypertrophy is associated with 'down regulation' of the EGF receptor.