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

为探讨维持正常通气量/灌流比的机制，用荧光染料同时测定了分离的猪支气管和肺动脉平滑肌细胞内[Ca^&lt；2+&gt；]_&lt；Cyt&gt；[Ca^&lt；2+&gt；]、Fura-2和收缩的水平。氟烷(1.0-4.0%)可剂量依赖性地抑制心肌细胞[Ca~(2+)]_(2+)的短暂抑制收缩。因此，抑制收缩的机制之一是抑制组胺对支气管平滑肌细胞[Ca~(2+)]、[Ca~(2+)]~(2+)和Gt~(2+)的影响。组胺收缩时，[Ca^&lt；2+&gt；]_&lt；Cyt&gt；呈现双相升高、一过性增大和紧张性升高。无细胞外钙离子时，组胺引起的收缩减少，细胞内[Ca^&lt；2+&gt；]_&lt；Cyt&gt；升高是短暂的。因此，组胺引起的气管平滑肌收缩既与细胞外钙有关，也与细胞内钙有关。氧和二氧化碳对肺动脉平滑肌的影响高浓度氧可使收缩和[Ca^&lt；2+&gt；]、Cyt&gt；增加。高浓度二氧化碳可抑制肺动脉收缩和[Ca~(2+)]、Cyt~(2+)的升高。由此推测，高浓度氧气和二氧化碳对肺动脉平滑肌收缩的影响可能是由于细胞内[Ca~(2+)]~(2+)的变化。

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.>