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 (p H(i)) in mesenteric arterioles of spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats was investigated using the fluorescent indica tor seminaphthorhodafluor c-SNARF-1 to measure pH(i). Although the pH( i) of arterioles from WKY varied directly with pH(o), that of SHR arte rioles varied inversely. This abnormal pH(i) regulation in SHR was cor rected by 50-mu M 5-(N-ethylisopropyl)amiloride (EIPA), V-max of H+ tr ansport in response to changing extracellular Na+ was higher in SHR th an in WKY, but K-m did not differ. The Hill coefficient for H+ transpo rt with respect to pH(i) was 1.69 in prehypertensive and 1.56 in hyper tensive SHR. These results indicate that the Na+/H+ exchanger is parti cularly hyperactive in mesenteric arterioles of SHR.