Effects of volatile anesthetics on contraction and intracellular Ca^<2+> in tracheal smooth muscle

为探讨维持正常通气/灌注比的机制，采用荧光染色法同时测定离体猪支气管和肺动脉平滑肌细胞内Ca^<2+>水平（[Ca^<2+>]_<cyt>）、fura-2和收缩。氟烷对支气管平滑肌的影响细胞外高K^+刺激支气管平滑肌。氟烷（1.0-4.0%）引起了[Ca^<2+>]_<cyt>短暂性抑制收缩的剂量依赖性抑制。因此，抑制收缩的机制之一是抑制[Ca^<2+>]_<cyt的增加。组胺对支气管平滑肌的作用研究了哮喘因子组胺和哮喘特效药咖啡因的作用。在组胺作用下收缩时，[Ca^<2+>]_<cyt>呈两相性升高，即短暂性大升高和继发性强直升高。在没有细胞外钙离子的情况下，组胺作用使[Ca^<2+>]_<cyt>的升高是一过性的。因此，组胺作用下气管平滑肌的收缩与细胞外和细胞内钙均有联系。氧和二氧化碳对肺动脉平滑肌的影响高浓度氧增强了肺动脉平滑肌收缩和[Ca^<2+>]_<cyt>的增加。另一方面，高浓度二氧化碳抑制肺动脉平滑肌收缩和[Ca^<2+>]_<cyt>的增加。因此，我们推测高浓度氧气和二氧化碳对肺动脉平滑肌收缩的影响是由于[Ca^<2+>]_<cyt.>的变化所致

In order to investigate the mechanisms of preserving the normal ventiration/perfusion ratio, the cytosolic Ca^<2+>level ([Ca^<2+>]_<cyt>) by means of a fluorecence dye, fura-2 and contraction were measured simultaneusly in the isolated porcine bronchial and pulmonary arterial smooth muscle.Effects of halothane on bronchial smooth muscle Bronchial smooth muscles were stimulated with high extracellular K^+. Halothane (1.0-4.0%) caused dose-dependent depressions of the [Ca^<2+>]_<cyt> transient depressing contraction. Therefore, one of the mechanisms depressing contraction is the inhibition of increase in [Ca^<2+>]_<cyt.>Effects of histamine on bronchial smooth muscle The effects of histamine, a facter of asthma, and caffeine, a special remedy of asthma, is investigated. At the contraction by histamine, [Ca^<2+>]_<cyt> showed biphasic increase, transient large one and following tonic one. Without extracellular calcium ion, the contraction was decreased and the increase in [Ca^<2+>]_<cyt> was transient by histamine. Therefore, the contraction of tracheal smooth muscle by histamine heve connection with both extracellular and intracellular calcium.Effects of oxygen and carbon dioxide on pulmonary arterial smooth muscle High concentration oxygen reinfoce the increase in both contraction and [Ca^<2+>]_<cyt> of pulmonary arterial smooth muscle. On the other hand, high concentration carbon dioxide inhibit the increase in both contraction and [Ca^<2+>]_<cyt> of pulmonary arterial smooth muscle. Therefore, it is seggested that the effect of high concentration oxygen and carbon dioxide on pulmonary arterial smooth muscle contraction is due to the change of [Ca^<2+>]_<cyt.>