Abstract
Recently, elimination of CBG has been reported to result in higher binding affinity of corticosterone (B) to mineralocorticoid receptor(MR). We have studied binding affinities of rat kidney MR by cytosol and tissue slice methods after complete perfusion in situ. To estimate the degree of serum contamination in the cytosol, rat serum CBG and albumin level in cytosol were assayed by RIA. Perfused kidney cytosol contained less than 0.1 ul per ml serum contamination. In cytosol and slice experiments without blockade of the glucocorticoid receptor (GR), both Type I and II 3H-aldosterone binding sites were present, indicated by the curvilinear pattern of Scatchard analysis. With RU-28362 as GR blockade, Scatchard plots were rectilinear. In perfused cytosol, all the corticosteroids tested (aldosterone, deoxycorticosterone, B, cortisol, dexamethasone) bound to MR with the same affinity in the presence of RU-28362, while non-perfused cytosol showed steroid specificity similar to those previously reported. Addition of increasing amount of rat serum to perfused cytosol decreased the binding of B to MR, indicating that B was bound to CBG, thus decreasing the availability of B for MR-binding. Slices of well-perfused kidney showed steroid specificities similar to the non-perfused cytosol.
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Sasano, H., Martin, K. & New, M. 492 STEROID SPECIFICITY OF RAT RENAL MINERALOCORTICOID RECEPTORS AFTER IN SITU PERFUSION. Pediatr Res 19, 192 (1985). https://doi.org/10.1203/00006450-198504000-00522
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DOI: https://doi.org/10.1203/00006450-198504000-00522