Autoradiographic localization of binding sites for oxytocin and vasopressin in the rat kidney

The distribution of [3H]vasopressin- and [3H]oxytocin-binding sites was examined, using an autoradiographical technique, in the kidney of Long-Evans and Brattleboro rats. Two types of binding sites with affinities in the nanomolar range were detected: one, located on glomeruli, bound both vasopressin and oxytocin; the other, on collecting ducts, bound vasopressin selectively. In the presence of 10 mumol oxytocin/l, [3H]vasopressin labelling was abolished in glomeruli, but only reduced in collecting ducts; [3H]oxytocin labelling was completely abolished by 10 mumol vasopressin/l. These observations are discussed in relation to known effects of neurohypophysial hormones on renal physiology.