Autoradiographic localization of corticosterone receptors (type III) to the collecting tubule of the rat kidney.

Recently, a class of receptors exhibiting high affinity for corticosterone was described in rat kidney (Feldman, D. et al., Endocrinology 92: 1429, 1973). These receptor sites exhibited negligible affinity for dexamethasone and aldosterone and were designated Type III to distinguish them from sites having high affinity for aldosterone (Type I), and sites with high affinity for dexamethasone and corticosterone (Type II). To visually localize Type III sites in the kidney and demonstrate whether or not they represent intracellular steroid receptors, we used an autoradiographic procedure for diffusible substances. Male adrenalectomized rats were injected intravenously with the following combination of steroids per 100 g body weight: 4 × 10–9 mol [3H]corticosterone, 4 × 10–9 mol unlabeled aldosterone, and 4 × 10–8 mol unlabeled dexamethasone. To differentiate “nonspecific” binding, each experimental animal was paired with a control animal that received the same steroids plus 250-fold unlabeled corticosterone. ...