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

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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.>