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Autori: Dospinescu C and Cruickshank SF
Editorial: J Mol Cell Cardiol, 40(6), p.1015, 2006.
Small pulmonary arteries (SPA) and veins contract when alveolar pO2 is low. Hypoxic pulmonary vasoconstriction (HPV) is known to release Ca2+ from the SR in SPA. Hypoxia-induced SR Ca2+ release activates ClCa. Agonist-induced contraction in SPA increases when [Cl-]0 is reduced. However, the effects of altering Cl- flux on HPV in the pulmonary vein are not known. Here we show how changes in extracellular Cl- differentially affect SPA and venular contraction to hypoxia.
Using dual wire myography, the hypoxic responses of small porcine intrapulmonary arteries and veins (4th to 5th generation; 500-900 um outer diameter) were compared and the effect of decreasing extracellular Cl- on the hypoxic response determined. Baseline tension was determined in preliminary experiments and contractions are expressed as a percentage of control (80 mM KCl). Data are presented as means ± SEM. Statistical differences were determined using Student’s t tests with P < 0.05 being considered significant. Hypoxia (PO2 < 25 mm Hg) induced contractions in both veins and arteries (43.5 ± 4.5% and 13.4 ± 3.6%, respectively). Decreasing extracellular Cl- did not significantly affect hypoxia-induced contractions of vein (low-Cl- = 38.9 ± 5.5% vs. control, P > 0.05, n = 9) but did enhance responses in the arteries to 41.5 ± 9.8% (P < 0.05, n = 6).These results suggest that Cl- flux plays a role in the HPV response in SPAs, but not in veins. Further work on isolated pulmonary myocytes is needed to elucidate the role of ClCa in determining membrane potential under normoxic and hypoxic conditions.
Cuvinte cheie: hypoxic pulmonary vasoconstriction