NHE-1 PROTEIN IN VASCULAR SMOOTH-MUSCLE AND LYMPHOCYTES FROM THE SPONTANEOUSLY HYPERTENSIVE RAT

The present study examined the abundance of NHE-1 protein in cultured vascular smooth muscle cells (VSMCs), freshly isolated thymocytes, and fresh aortic tissue from spontaneously hypertensive rats (SHRs) and a ge-matched Wistar-Kyoto (WKY) rats. Two sets of affinity-purified anti bodies (Ab((765-778)) and Ab((698-711))) against different epitopes of the NHE-1 isoform of the Na+-H+ antiporter were used. Each set of ant ibodies recognized a major protein band at 105 to 110 kD that was mon abundant in protein lysates prepared from cultured VSMCs from the SHR than those from WKY rats (Ab((765-778)) 0.047+/-0.011 vs 0.010+/-0.002 O.D. units/10 mu g protein, P<.001 for SHR and WKY, respectively; and Ab((698-711)) 0.173+/-0.026 vs 0.087+/-0.028 O.D. units/10 mu g prote in, P<.05, for SHR and WKY, respectively). The increase in NHE-1 prote in abundance in cultured VSMCs from the SHR was associated with a grea ter V-max of the Na+-H+ antiporter as compared to those from WKY rats (17.93+/-2.07 vs 8.16+/-1.05 mmol H+/min, P<.001, respectively). In co ntrast to cultured VSMCs, there was no difference in the relative abun dance of NHE-1 protein in fresh aortic tissue (0.075+/-0.018 vs 0.083/-0.017 O.D. units/10 mu g protein, from SHR and WKY, respectively) or in freshly isolated thymocytes (0.158+/-0.046 vs 0.226+/-0.054 O.D. u nits/10 mu g protein, from SHR and WKY, respectively). We conclude tha t the increase in the V-max of the Na+-H+ antiporter in cultured VSMCs from the SHR, compared to those from WKY rats, is due, at least in pa rt, to increased levels of NHE-1 protein.