Abstract
Effects of the low temperature and of the electrical square wave stimulation on spontaneous contractions of isolated guinea-pig atria and the influence of thiamine tetrahydrofurfuryldisulfide (TTFD) on these effects were investigated and the following results were obtained:
1) Atrial spontaneous contractions were arrested within 15 minutes by the change of temperature in the medium from 30 to 20°C. When TTFD was added to the medium at concentrations higher than 10-5g/ml one hour before the temperature change, the contractions were not arrested even at 30 minutes after the change of the temperature.
2) The arrhythmic contractions were induced on the rhythmic contractions of isolated atria by the electrical square wave stimulation given at a duration of 5 msec., at 120 cycles per minute, and at several critical intensities. When TTFD was added to the medium at concentration of 10-4g/ml one hour before the stimulation, the critical intensity to induce the arrhythmic contractions was increased by the presence of the drug.
3) The influences of TTFD on the responses of atrial tissue against these two kinds of extrinsic physical stimulations were seen even at 30 minutes after the drug was washed out from the bath fluid, when the isolated atria had been pre-incubated with the drug at the same concentration for one hour before the temperature change of the medium or the stimulation by the electrical square wave.
From these results, it was assumed that TTFD might reveal these effects through the stabilization of the tissue membrane.
