Influence of Magnesium on the β-Inhibition of Catecholamines in the Uterine Circular Muscle of Estrogen-treated Rats

抄録

The effects of Mg and isoprenaline on the uterine circular muscle of ovariectomized rats which were injected with estradiol for 2-6 days were investigated. The muscle strip exhibited an action potential that was composed of a spike and a plateau, and also exhibited a twitchlike contraction due to electrical stimulation. The duration of the action potential became longer when the treatment with estrogen was applied until the maximal effect was built up in 4-5 days. Both the duration of the action potential and the amplitude of contraction were reduced when isoprenaline was applied. When Mg (0.5 mm) was added to the bathing solution these β-effects were progressively potentiated and the maximal effect was obtained in about 1 hr. An increase in membrane conductance was induced by the application of isoprenaline in a control Locke solution and it was further accelerated by exposure to Mg-containing solution. The possibility that the β-action is potentiated by Mg ions which penetrated into the membrane is concluded.