Abstract
In order to reevaluate the effects of thiamine and its derivatives in large dosis on heart muscle, the following experiments on the isolated toad heart were performed.
1. Using Yagi's apparatus of recycling, the action on the contractile power was observed. It was confirmed that thiamine-HCl, thiamine propyl disulfide (TPD), thiamine tetrahydrofurfuryl disulfide (TTFD), thiamine disulfide and oxythiamine increased the contractile power. Especially, in the concentration of 1.4mM, the action of TPD and TTFD was so pronounced that approximately doubled values of the contractile deflection, cardiac output and aortic pressure were recorded. However, thiamine diphosphate showed no action during the period of time tested. Thiaminic acid showed even the inhibitory action.
2. In the concentration of 1.4mM, TPD caused the prolongation of latent period and repolarization phase of transmembrane action potential.
3. The oxygen consumption of recycling toad heart was measured manometrically with a modified Warburg chamber. When the contractile power increased on the administration of TPD, the cardiac efficiency did not diminish in spite of the increase of oxygen consumption.
