Chronic hypoxia elevates intracellular pH and activates Na+/H+ exchange in pulmonary arterial smooth muscle cells.
Chronic hypoxia (CH), caused by many lung diseases, results in pulmonary hypertension due, in part, to increased muscularity of small pulmonary vessels. Pulmonary arterial smooth muscle cell (PASMC) proliferation in response to growth factors requires increased intracellular pH (pHi) mediated by activation of Na+/H+ exchange (NHE); however, the effect of CH on PASMC pHi homeostasis is unknown. Thus we measured basal pHi and NHE activity and expression in PASMCs isolated from mice exposed to normoxia or CH (3 wk/10% O2). pHi was measured using the pH-sensitive fluorescent dye BCECF-AM. NHE activity was determined from Na+-dependent recovery from NH4-induced acidosis, and NHE expression was determined by RT-PCR and immunoblot. PASMCs from chronically hypoxic mice exhibited elevated basal pHi and increased NHE activity. NHE1 was the predominate isoform present in mouse PASMCs, and both gene and protein expression of NHE1 was increased following exposure to CH. Our findings indicate that exposure to CH caused increased pHi, NHE activity, and NHE1 expression, changes that may contribute to the development of pulmonary hypertension, in part, via pH-dependent induction of PASMC proliferation.
Rios
Eon J
EJ
Division of Pulmonary and Critical Care Medicine, Johns Hopkins Univ., Baltimore, MD 21224, USA.
Fallon
Michele
M
Wang
Jian
J
Shimoda
Larissa A
LA
D000818:Animals; D001483:Base Sequence; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D002908:Chronic Disease; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D006976:Hypertension, Pulmonary / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017380:Hypertrophy, Right Ventricular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D066298:In Vitro Techniques; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009131:Muscle, Smooth, Vascular / Q000378:metabolism* / Q000473:pathology; D011651:Pulmonary Artery / Q000378:metabolism* / Q000473:pathology; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
D027682:Cation Transport Proteins; D008565:Membrane Proteins; C490997:Slc9a1 protein, mouse; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers