Influence of extracellular pH on intracellular pH in arterioles and skeletal muscle of spontaneously hypertensive and Wistar-Kyoto rats

The effect of changing extracellular pH (pH(o)) on intracellular pH (pH(i)) in mesenteric arterioles of spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats was investigated using the fluorescent indicator seminaphthorhodafluor c-SNARF-1 to measure pH(i). Although the pH(i) of arterioles from WKY varied directly with pH(o), that of SHR arterioles varied inversely. This abnormal pH(i) regulation in SHR was corrected by 50-mu M 5-(N-ethylisopropyl)amiloride (EIPA), V-max of H+ transport in response to changing extracellular Na+ was higher in SHR than in WKY, but K-m did not differ. The Hill coefficient for H+ transport with respect to pH(i) was 1.69 in prehypertensive and 1.56 in hypertensive SHR. These results indicate that the Na+/H+ exchanger is particularly hyperactive in mesenteric arterioles of SHR.