Testosterone treatment restores reduced vasopressin-binding sites in the kidney of the ageing rat

Abstract

Young, middle-aged and aged rats received s.c. testosterone implants for 50-52 days in order to investigate whether supplementation of testosterone in aged rats could normalize the reported reduction of kidney arginine vasopressin (AVP)-binding sites and increase the plasma concentration of AVP. Receptor number, which was measured by means of a membrane-binding assay with [3H]AVP as ligand, was below the detection level in the untreated aged rat. Following testosterone treatment, no effects were seen in the youngest groups, but in the aged group AVP receptors became clearly detectable, albeit with a lower affinity. A remarkable observation was the increase in affinity for renal AVP binding in the middle-aged compared with the young rat. Plasma levels of AVP in control aged rats tended to be higher. Such a tendency was completely absent in the testosterone-treated aged rats. Possible mechanisms underlying the restoration of reduced AVP-binding sites in the kidney of the aged rat by testosterone treatment are discussed.