Sodium–hydrogen antiporter protein in normotensive Wistar–Kyoto rats and spontaneously hypertensive rats

Objective To examine the mechanism of increased Na–H antiport activity in tissues of the spontaneously hypertensive rat (SHR) by measuring the amount of sodium–hydrogen exchanger isoform 1 (NHE-1) in cultured vascular and striated muscle cells, and in ex vivo tissue extracts of membranes from the brain, heart, kidney and skeletal muscle. Methods A polyclonal rabbit antibody was raised against a fusion protein consisting of a section of the carboxyl tail of NHE-1 and β-galactosidase. Cell extracts were separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, and proteins were transferred to supported nitrocellulose. NHE-1 was detected by Western blotting and quantified by densitometry. Results Cultured aortic and striated muscle cells from SHR contained similar amounts of NHE-1 on Western blots to those from control Wistar-Kyoto (WKY) rat cells. Ex vivo extracts of crude membranes from SHR tissues also contained quantities of NHE-1 similar to those from WKY rat tissues. Conclusion The increased Na–H antiport activity observed in SHR cells in vitro and in vivo is not due to an increased amount of NHE-1 protein in SHR cells. This suggests that in this model of hypertension the increased transport activity results from an increased turnover number per NHE-1 molecule.