カリウムおよびナトリウム異常環境下における心房律動におよぼすThiamine tetrahydrofurfuryldisulfide(TTFD)とStrophanthin-Gの作用の比較研究

Abstract

In our previous paper we had reported the antiquinidine effect of thiamine tetrahydrofurfuryldisulfide (TTFD) on atrial contractions in guinea-pigs. In the presented experiments, the effects of TTFD in abnormal inorganic ions milieux were investigated in comparison with the effects of strophanthin-G.(1) In a high K Locke's solution, the atrial contractions were arrested and were thereafter restored by the addition of TTFD 10-4 to 2×10-4(g/ml ) if the arresting concentration of potassium in the solution was at minimum.(2) The suppression of atrial contractions in K-free Locke's solution was promoted by the addition of TTFD 10-4, but the arrhythmic contractions in 1/4 K Locke's solution become rhythmic by addition of TTFD 10-4, though the positive inotropic and negative chronotropic effects of TTFD in this solution were weaker than those in a normal Locke's solution.(3) Strophanthin-G 10-6 could restore the arrested atrial contractions in a high K Locke's solution. In a low K Locke's solution, strophanthin-G arrested the atrial contractions more quickly than in a normal or high K Locke's solution, though its positive inotropic effect in a low K Locke's solution was more remarkable than in a normal Locke's solution.(4) The atria in a normal Locke's solution responded normally to adrenaline even after the atria had been kept in a 40% Na Locke's solution for two hours, whereas the atria responded weakly to the drug if they had been kept in a K-free Locke's solution for a half hour. When sodium dialysed atria contract in a normal Locke's solution, the atria are assumed to be immersed in a relatively high Na Locke's solution, despite the difficulty in preparing an sotonic high Na solution for experimental purposes.(5) The effects of TTFD on atrial contractions both in low and in relatively high Na Locke's solutions were similar to those of TTFD in a normal Locke's solution. The effect df strophanthin-G in a low Na Locke's solution to that of the same drug in a normal Locke's solution, but that of strophanthin-G in a relatively high Na Locke's solution was similar to that of the same drug in a low K Locke's solution.From these experimental results it is concluded that the antiquinidine effect of TTFD may be attributed to the decrease of potassium influx or the increase of potassium efflux of the atria.