IMMUNOHISTOCHEMICAL LOCALIZATION OF RENAL MINERALOCORTICOID RECEPTOR BY USING AN ANTI-IDIOTYPIC ANTIBODY THAT IS AN INTERNAL IMAGE OF ALDOSTERONE

A monoclonal antibody (H10E), generated by an auto-anti-idiotypic procedure and directed at the aldosterone-binding site of mineralocorticoid receptor (MR), was used in immunohistochemical studies to localize MR in rabbit kidney preparations. In agreement with earlier physiological and biochemical observations, MR was detected in connecting and cortical collecting tubules. Additionally, MR was detected in the distal tubules, the medullary and papillary collecting ducts, and in the epithelial cells lining the papilla. The internal image properties of the antibody were exploited to assess the specificity of MR detection by means of competition studies with hormones and antihormones. Immunostaining was completely abolished by preincubation with aldosterone but not with RU 486, a steroid antagonist that does not bind MR. On the cellular level, immunostaining occurred in the cytoplasm and, in the majority of cells, in the nucleus as well. The nucleocytoplasmic distribution of MR was unaffected by adrenalectomy or by administration of aldosterone. The availability of this specific monoclonal antibody makes it feasible to study MR expression in other target tissues and in pathological disorders.