SPECIFIC ESTRADIOL-17-BETA BINDING-COMPONENT IN ADULT-RAT KIDNEY

An estradiol-17β (E2) binding component has been identified in adult rat kidney which exhibits characteristics of a specific receptor. Scatchard analysis of kidney cytosol revealed a single class of binding sites for E2, having high affinity (~0.6 × 1010 M) and limited binding capacity (12-20 fmol/mg protein). The eytosol macromolecule has a sedimentation coefficient of approximately 4S in either low or high salt (0.4 M KCl) sucrose density gradients. Competition studies using a 100-fold excess of various unlabeled steroids demonstrated greatest inhibition by various estrogens, with E2 and DES as the most effective competitors; whereas several androgens, aldosterone and progesterone inhibited binding very little. Incubation of kidney slices with [3H]-E2 resulted in localization of the steroid in purified nuclei. Addition of a 100-fold excess of unlabeled E2 or DES inhibited translocation of [3H]-E2 by 94 and 79% respectively, whereas testosterone, dihydrotestosterone and aldosterone exhibited only minimal inhibition on nuclear translocation of [3H]-E2 receptor. These data offer strong evidence for the existence of an E2 receptor in rat kidney. It remains to be determined which specific cellular events are regulated by E2 in the rat kidney. © 1979.