ADRENALECTOMY REDUCES ALPHA-1 AND NOT BETA-1 NA+-K+-ATPASE MESSENGER-RNA EXPRESSION IN RAT DISTAL NEPHRON

The abundance of mRNA of alpha1-, alpha2-, alpha3-, beta1-, and beta2-isoforms of Na+-K+-ATPase was examined in several renal structures of normal and adrenalectomized (ADX) rats. In situ hybridization with S-35-labeled cRNA probes was performed on kidney sections from adult rats. The number of silver grains per unit surface area was quantified over cells of the glomerulus, proximal convoluted tubules (PCT), early distal tubules (EDT), and cortical collecting ducts (CCD). In normal rat kidney, alpha1- and beta1-mRNA was detected in PCT, EDT, and CCD, with the following range of magnitude: EDT > CCD > PCT > glomerulus. The amount of alpha1- and beta1-mRNA was equivalent. A large abundance of these two mRNA species was also found in the medullary thick ascending limb of the loop of Henle. Expression of alpha2, alpha3, and beta2 was very low and evenly distributed over any cell type. In ADX, a significant decrease in alpha1-mRNA (30%) was observed in EDT and CCD, with no change in PCT. Beta1-mRNA abundance was unaffected by adrenalectomy. These results indicate that 1) in the rat kidney alpha1- and beta1-mRNA are coexpressed at a similar level that varies along the renal tubule according to the cell type, 2) minute expression of alpha2-, alpha3-, and beta2-mRNA is present in the kidney, and 3) corticosteroid depletion reduces the expression of alpha1- and not beta1-mRNA in the corticosteroid-sensitive tubular cells.