Endothelin-1 augments Na/H exchange activity in murine pulmonary arterial smooth muscle cells via Rho kinase. PLos One 7: e46303

Excessive production of endothelin-1 (ET-1), a potent vasoconstrictor, occurs with several forms of pulmonary hypertension. In addition to modulating vasomotor tone, ET-1 can potentiate pulmonary arterial smooth muscle cell (PASMC) growth and migration, both of which contribute to the vascular remodeling that occurs during the development of pulmonary hypertension. It is well established that changes in cell proliferation and migration in PASMCs are associated with alkalinization of intracellular pH (pHi), typically due to activation of Na +/H+ exchange (NHE). In the systemic vasculature, ET-1 increases pHi, Na +/H+ exchange activity and stimulates cell growth via a mechanism dependent on protein kinase C (PKC). These results, coupled with data describing elevated levels of ET-1 in hypertensive animals/humans, suggest that ET-1 may play an important role in modulating pHi and smooth muscle growth in the lung; however, the effect of ET-1 on basal pHi and NHE activity has yet to be examined in PASMCs. Thus, we used fluorescent microscopy in transiently (3–5 days) cultured rat PASMCs and the pH-sensitive dye, BCECF-AM, to measure changes in basal pHi and NHE activity induced by increasing concentrations of ET-1 (10210 to 1028 M). We found that application of exogenous ET-1 increased pHi and NHE activity in PASMCs and that the ET-1-induced augmentation of NHE was prevented in PASMCs pretreated with an inhibitor of Rh