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  • Title: Hypocapnia-induced contraction of porcine airway smooth muscle.
    Author: Lindeman KS, Croxton TL, Lande B, Hirshman CA.
    Journal: Eur Respir J; 1998 Nov; 12(5):1046-52. PubMed ID: 9863995.
    Abstract:
    Hypocapnia constricts peripheral airways in vivo. This study investigated the role of airway smooth muscle in this phenomenon and the mechanism of hypocapnia-induced contraction in vitro. Isometric tension, intracellular pH (pHi) and intracellular free calcium concentration ([Ca2+]i) were measured in porcine airway smooth muscles suspended in organ baths in the presence of 5% or 0% CO2. In tracheal strips precontracted with carbachol, hypocapnic challenge (0% CO2) produced increases in tension, pHi, and [Ca2+]i. In bronchial rings or tracheal strips precontracted with carbachol, nifedipine administered between consecutive contractions attenuated responses to hypocapnia (75+/-11% above carbachol-precontracted tension before nifedipine versus 39+/-9% after nifedipine, n=7 bronchial rings, p<0.05). Neither indomethacin (5 microM), nordihydroguaiaretic acid (10 microM) nor phenidone (10 microM) significantly altered responses. These data suggest that enhanced Ca2+ influx through voltage-dependent Ca2+ channels of airway smooth muscle cells is important in airway responses to hypocapnia.
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