Biological and Pharmaceutical Bulletin
Online ISSN : 1347-5215
Print ISSN : 0918-6158
ISSN-L : 0918-6158
Mechanism of Tachyphylaxis on the Inhibitory Effect of Manganese on Agonist-Induced Contractions in the Isolated Vas Deferens of the Guinea Pig
牛島 ひろみ五味 保男
ジャーナル フリー

1995 年 18 巻 2 号 p. 246-250


In the isolated vas deferens of the guinea pig, the inhibitory effect of manganese (Mn2+) on contractions induced by norepinephrine decreased when the contractions were induced repeatedly in the presence of Mn2+. This phenomenon, "tachyphylaxis" to the inhibitory effect of Mn2+, was minimally observed when contractions were induced by acetylcholine. Contractions induced by acetylcholine as well as by norepinephrine in a Mn2+-free medium were augmented in preparations in which manganese had accumulated intracellularly by repetitive applications of high potassium in the presence of Mn2+. The magnitudes of their augmentation were dependent on the manganese contents of the preparations. The augmented contractions were remarkably resistant to the inhibitory effect of Mn2+ applied to the medium. These results suggest that intracellular manganese augments the contractions and this augmentation results in an apparent decrease in the inhibitory effect of Mn2+ in the medium.

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