SODIUM-DEPENDENT, ETHYLISOPROPYLAMILORIDE-SENSITIVE MECHANISMS REGULATE INTRACELLULAR PH IN HUMAN VASCULAR SMOOTH-MUSCLE

1. The pH‐sensitive dye 2,7‐biscarboxy‐ethyl‐5(6)‐carboxyfluorescein (BCECF) was used to examine the contribution of Na+‐H+ exchange and bicarbonate‐dependent processes to intracellular pH (pHi) regulation in cultured human vascular smooth muscle. 2. The recovery of pHi following an NH4Cl‐induced acidosis was Na+‐dependent and could be inhibited by ethylisopropylamiloride (200 μmol/L). Recovery was unaffected by the anion exchange inhibitor 4‐acetamido‐4′‐isothio‐cyano‐stilbene‐2,2′‐disulfonic acid (200 μmol/L). 3. Recovery from intracellular acidosis was more rapid when bicarbonate ions were present in the extracellular medium. 4. The results suggest that Na+‐H+ exchange as well as an Na+‐dependent bicarbonate process, which can be inhibited by ethylisopropylamiloride, can influence the ability of smooth muscle to recover from intracellular acidosis. Copyright © 1990, Wiley Blackwell. All rights reserved