[Role of intracellular Ca-depots in the mechanism of action of caffeine on excitation-contraction coupling in the frog myocardium].
Caffeine inotropic effects on frog atrial and ventricular muscle were studied under different patterns of stimulation. It was found that in the course of repetitive stimulation (0.5/s) caffeine produced transient potentiation and following inhibition of contractions which were accompanied by an increase in the rate of tension development, a decrease of the time to peak tension, an increase in relaxation duration and a decrease in the relaxation rate. Caffeine reduced the increment of contraction amplitude in Bowdich staircase under stimulation of the heart muscle with a series of impulses. It was concluded that caffeine caused the depletion of calcium in the intracellular stores. On the basis of literature and our data a scheme was proposed to account for two-phase caffeine action on the frog myocardium. According to this scheme caffeine acts simultaneously on both stages of excitation-contraction coupling: it alters calcium current and prevents Ca accumulation in the intracellular stores.
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006325:Heart Atria; D006352:Heart Ventricles; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D011895:Rana ridibunda; D011896:Rana temporaria; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
D002110:Caffeine; D002118:Calcium
Rol' vnutrikletochnykh Ca-depo v mekhanizme deĭstviia kofeina na sopriazhenie vozbuzhdeniia i sokrashcheniia v miokarde liagushki.