Ikezawa K, Takenaga H, Irie K, Sato M, Nakajima H, Kiyomoto A
Nihon Yakurigaku Zasshi. 1978 Oct;74(7):805-18.
Bronchodilating action of l-MTI was investigated by intravenous administration to anesthetized animals and the results were compared to those seen with isoproterenol. Bronchoconstriction was induced by histamine or serotonin. Under pentobarbital anesthesia, the bronchodilating activity of l-MTI was approx. 1/20 that of isoproterenol in cats and dogs, but less than 1/100 that of isoproterenol in monkeys and guinea pigs. The results indicate that the bronchodilating activity of l-MTI is variable and species dependent. It was demonstrated, however, that in guinea pigs, l-MTI did not produce any bronchodilating activity, when the animals were anesthetized with urethane. The absence of the bronchodilating response in animals under this anesthesia was also seen in vagotomized, adrenalectomized and reserpinized, norepinephrine-infused guinea pigs. On the contrary, l-MTI exhibited the bronchodilating action in reserpinized, pithed or hexamethonium-treated guinea pigs anesthetized with urethane. On th other hand, isoproterenol produced a bronchodilating action in all preparations mentioned above. It was also evident that l-MTI suppressed the bronchodilating action of isoproterenol in pentobarbital anesthetized guinea pigs. In addition, l-MTI increased the heart rate of guinea pigs with a low beating rate, but decreased it when the control rate was high. These results suggest that at least in guinea pigs, l-MTI acts as a partial agonist and that the effect of l-MTI on the bronchial system depends on the sympathetic tone and/or sympathetic bronchodilator reflex, as proposed by McCULLOCH ET AL. (9).
通过对麻醉动物静脉注射来研究左旋MTI的支气管扩张作用，并将结果与异丙肾上腺素的结果进行比较。用组胺或血清素诱导支气管收缩。在戊巴比妥麻醉下，左旋MTI在猫和狗中的支气管扩张活性约为异丙肾上腺素的1/20，但在猴子和豚鼠中小于异丙肾上腺素的1/100。结果表明，左旋MTI的支气管扩张活性是可变的且依赖于物种。然而，已证明，在用氨基甲酸乙酯麻醉的豚鼠中，左旋MTI不产生任何支气管扩张活性。在迷走神经切断、肾上腺切除、利血平化并用去甲肾上腺素灌注的豚鼠中，也观察到在这种麻醉下动物缺乏支气管扩张反应。相反，左旋MTI在利血平化、去脑或用六甲铵处理并用氨基甲酸乙酯麻醉的豚鼠中表现出支气管扩张作用。另一方面，异丙肾上腺素在上述所有制剂中均产生支气管扩张作用。同样明显的是，左旋MTI在戊巴比妥麻醉的豚鼠中抑制了异丙肾上腺素的支气管扩张作用。此外，左旋MTI使心率低的豚鼠心率增加，但在对照心率高时使其心率降低。这些结果表明，至少在豚鼠中，左旋MTI起部分激动剂的作用，并且如McCULLOCH等人（9）所提出的，左旋MTI对支气管系统的作用取决于交感神经张力和/或交感神经支气管扩张反射。
