STUDIES ON THE AUTOMATISM (II):EFFECTS OF Ca++ AND Mn++ ON THE FLUCTUATION POTENTIAL OF THE PACEMAKER CELL

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Pacemaker cells of an isolated sinus node of guinea pig were exposed to K-free or ouabain Krebs solution and effects of Ca++ and Mn++ on the fluctuation potential of the pacemaker cell were examined. Potentials were recorded by means of a conventional microelectrode technique. The sinus node tissue closed to the crista terminalis was trimmed to 1 × 0.5mm area including the dominant pacemaker cells. The tissue was transported into a bath of 1.0ml capacity filled with the standard Krebs solution saturated with a gas mixture of 95% O2 and 5% CO2. 1) When the pacemaker cells were perfused in the K-free or ouabain Krebs solution, they showed the fluctuation potential on depolarizing (under-40mV). 2) The fluctuation potential was increased by application of isoproterenol. 3) The fluctuation potential was decreased in the Ca-free Krebs solution. 4) The fluctuation potential was inhibited by applying the Mn-Krebs solution. In conclusion these fluctuation potentials would be deprived from Na-Ca exchange when the Na-K pump was depressed by the K-depletion or ouabain application.
北関東医学会の論文