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Enhanced Ca2+‐activated Cl− conductance and TMEM16A expression in pulmonary arterial smooth muscle in a rat model of chronic hypoxic pulmonary hypertension
Author(s) -
Sun Hui,
Li Anlong,
Paudel Omkar,
Lo Alexander K.,
Yang XiaoRu,
Sham James S.K.
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.861.11
Subject(s) - niflumic acid , chemistry , hypoxia (environmental) , pulmonary hypertension , endocrinology , medicine , patch clamp , downregulation and upregulation , receptor , biochemistry , organic chemistry , oxygen , gene
Ca 2+ ‐activated Cl − Channel (CaCC) encoded by TMEM16A plays an important role in the regulation of vascular tone. Here we sought to determine whether TMEM16A expression and CaCC currents (I Cl.Ca ) in pulmonary arterial smooth muscle cells (PASMCs) are altered in a rat model of chronic hypoxic pulmonary hypertension (CHPH). TMEM16A mRNA was quantified by qRT‐PCR and protein by immunoblotting. I Cl.Ca was recorded using whole‐cell or perforated patch clamp technique under K + free conditions. The TMEM16A mRNA was more abundant in pulmonary arteries (PA) compared to cerebral, tail, mesenteric and renal arteries in normoxic rats. In Fluo‐3/AM‐loaded PASMCs, caffeine‐induced Ca 2+ release evoked robust outward currents at 0 mV (19.9±2.4 pA/pF) and inward current at −80 mV (−21.7±3.1 pA/pF). The current was inhibited by niflumic acid, and reversed at the predicted E Cl following the changes of [Cl − ] gradient, as consistent with I Cl.Ca . Chronic hypoxia (10% O 2 , 4 weeks) caused an increase in I Cl.Ca density evoked by caffeine (30.0 ± 6.8 pA/pF at 0 mV) or by depolarization with [Ca 2+ ] i clamped at 750 nM (124.2 ± 24.1 vs. 24.4 ± 3.3 pA/pF at +120 mV) in PASMCs, accompanied by ~ 2‐fold increase in TMEM16A mRNA and 5‐fold increase in protein levels in PA. Our results show that TMEM16A and functional CaCC are highly expressed in rat PA. Their upregulation by hypoxia may contribute to the enhanced pulmonary vasoconstriction observed in CHPH.