[Receptors of steroid hormones in the kidney]

Several steroid hormones act in the kidney. We have examined, by autoradiography, the precise distribution of receptors for aldosterone, glucocorticoids, vitamin D (1-25(OH)2D3) and estrogens, in the different epithelia of the nephron isolated by microdissection. Specific nuclear binding sites are localized in the distal parts of the nephron, with some variations according to the steroid hormone considered: target cells for aldosterone are located in the distal tubule and cortical collecting duct, glucocorticoid receptors are present in all distal segments, whereas those of 1-25(OH)2D3 are restricted to the thick ascending limb of Henle's loop and to the medullary collecting tubule. Thus, it appears that several receptors coexist in some cell types. No specific nuclear binding sites for estrogens could be detected along the nephron. On the other hand, a non nuclear specific binding for glucocorticoids was observed in the proximal tubule, where specific glucocorticoid effects have been described. By autoradiography on intact target cells, it appeared that aldosterone receptors are essentially (or exclusively) located in nuclei, as was recently described for other steroid hormones. Binding sites for aldosterone are already present in its target cells in the fetal kidney before their functional differentiation. Aldosterone is weakly metabolized in the kidney, without specific tubular localization. It is possible to show some modifications of aldosterone binding sites, at the level of its target cells, in some pathological states, such as hypertension.