Intracellular Cl‐concentration is increased in pulmonary arterial myocytes associated with chronic hypoxic pulmonary hypertension

Abstract

Intracellular Cl− plays an important role in the regulation of contraction and proliferation of vascular smooth muscle. Yet little is known about the intracellular Cl− concentration ([Cl−]i) in pulmonary arterial smooth muscle cells (PASMCs), and whether it is altered in disease states such as chronic hypoxic pulmonary hypertension (CHPH) remains unknown. The present study was undertaken to address these issues. CHPH was induced by exposing rats to 10% O2 for 3 weeks. Gramicidin‐perforated patch clamp technique was used to measure the reversal potential (Erev) of caffeine‐induced Ca2+‐activated Cl− current (ICl Ca) in PASMCs with intact intracellular Cl−, and the [Cl−]i was calculated using Nernst equation. Caffeine‐induced currents and niflumic acid‐sensitive caffeine‐induced currents elicited by voltage ramps from −70 to +70 mV reversed at closely similar voltages in the same cell, suggesting that the caffeine‐induced current is mainly ICl Ca. The Erev of ICl Ca measured in hypoxic cells was more positive than that obtained from normoxic cells (−23.7±0.8, n=36 vs. −29.1±0.9 mV, n=33, p<0.001), giving rise to a higher [Cl−]i in hypoxic cells compared to controls (59.7±1.9 vs. 48.2±1.7 mM, p<0.001). Our results confirm that the [Cl−]i in PASMCs is well above equilibrium with resting potential, and reveal for the first time that the [Cl−]i is altered in PASMCs associated with CHPH. (Supported by NIH and AHA)