Adrenalectomy reduces alpha 1 and not beta 1 Na(+)-K(+)-ATPase mRNA expression in rat distal nephron

The abundance of mRNA of alpha 1-, alpha 2-, alpha 3-, beta 1-, and beta 2-isoforms of Na(+)-K(+)-ATPase was examined in several renal structures of normal and adrenalectomized (ADX) rats. In situ hybridization with 35S-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, alpha 1- and beta 1-mRNA was detected in PCT, EDT, and CCD, with the following range of magnitude: EDT > CCD > PCT > glomerulus. The amount of alpha 1- and beta 1-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 alpha 2, alpha 3, and beta 2 was very low and evenly distributed over any cell type. In ADX, a significant decrease in alpha 1-mRNA (30%) was observed in EDT and CCD, with no change in PCT. beta 1-mRNA abundance was unaffected by adrenalectomy. These results indicate that 1) in the rat kidney alpha 1- and beta 1-mRNA are coexpressed at a similar level that varies along the renal tubule according to the cell type, 2) minute expression of alpha 2-, alpha 3-, and beta 2-mRNA is present in the kidney, and 3) corticosteroid depletion reduces the expression of alpha 1- and not beta 1-mRNA in the corticosteroid-sensitive tubular cells.