Activity and Expression of Na+-H+ Exchanger Isoforms 1 and 3 in Kidney Proximal Tubules of Hypertensive Rats

Abstract Increased activity of the cellular Na+-H+ exchangers (NHEs), especially isoform 1 (NHE-1), is a recognized intermediate phenotype of hypertension. NHE activity has been demonstrated to be increased in proximal tubules of the spontaneously hypertensive rat (SHR). However, with the recent cloning of other members of this family of transporters, it is unclear which isoforms may contribute to this increased activity. We have used specific antibodies raised against glutathione-S-transferase fusion proteins of rat NHE-1 and NHE-3 to determine the relative contributions of these isoforms to the NHE activity in freshly isolated and cultured proximal tubule cells from SHR and Wistar-Kyoto (WKY) normotensive control rats. In freshly isolated proximal tubule cells, NHE activity was elevated almost 3-fold in SHR cells (P<.001), and in both rat strains, the contribution from NHE-1 and NHE-3 was approximately equal. Western blots of membranes from these cells showed equal amounts of NHE-1 protein in SHR and WK...