Catecholamine receptor binding in rat kidney: effect of aging.

Binding to several receptors was compared in kidneys from 3- and 24-month-old rats. In crude membrane preparations of aged rat kidneys, the number of beta 2-adrenergic receptors was significantly reduced but the number of total beta-adrenoceptors was unchanged. The high-affinity alpha 1-adrenoceptor component was significantly reduced in old rats, whereas the low-affinity component was unchanged. The number of alpha 2-adrenoceptors showed a non-significant decrease. 3H-spiperone binding sites were similar in young and old rats. For each receptor binding the KD values were the same in young and old animals. The D1 dopamine receptor was significantly reduced in old rats. In our experiments, age-related changes of specific binding sites in the kidney were selective for some receptors studied and did not seem to be due to general aging-induced membrane modifications. Moreover, the renal and central receptors were sensitive to aging differently in the same animal model.