DISTRIBUTION OF MINERALOCORTICOID AND GLUCOCORTICOID RECEPTOR MESSENGER-RNA ALONG THE NEPHRON

In the present study, a competitive polymerase chain reaction (PCR) te chnique was used to quantitate the relative levels of mineralocorticoi d receptor (MR) and glucocorticoid receptor (GR) mRNA in microdissecte d nephron segments from the rat kidney and of MR mRNA from isolated pr incipal and intercalated collecting duct cells from rabbit. RNA was is olated from cells and isolated tubules, cDNA was synthesized, and rece ptor cDNA was coamplified by PCR with a competitive control template. Beta-actin PCR products were also obtained from each nephron segment s tudied, to assess variations in RNA extraction and cDNA synthesis. MR mRNA, as determined by this competitive PCR technique, was 10-fold mor e abundant in cortical collecting duct (CCD), outer medullary collecti ng duct, and inner medullary collecting duct segments than in the prox imal tubule and thick ascending limb segments (P < 0.05). Both princip al and beta-intercalated cells of the CCD contained detectable levels of MR mRNA, although the levels in the principal cells were threefold higher (P < 0.01). GR mRNA was twofold more abundant in glomeruli, pro ximal tubule, and thick ascending limb segments than in the collecting duct segments (P < 0.05). In general, the distribution pattern of MR and GR mRNA is consistent with the distribution of adrenal corticoster oid function along the nephron.