Effects of low temperature and electrical (square wave) stimulation on spontaneous contractions in isolated guinea pig atria and influence of thiamine tetrahydrofurfuryl disulfide (TTFD) on these effects.

The spontaneous contractions of isolated guinea pig atria were arrested by a temperature change in the medium for 30 to 20 degrees C within 20 min. 2. When thiamine tetrahydrofurfuryl sulfide (TTFD) at concentration of 10-5 g/ml was added in the medium, the arrest was not seen for more than 30 min. 3. Arrhythmic contractions induced by the electrical square wave stimulation of threshold intensity were prevented by TTFD at 10-4 g/ml which was added to the medium. 4. These effects of TTFD at respective concentrations were seen even 30 min after the drug was removed from the medium, when the atria had been pre-incubated with the drug for one hour before the removal. 5. From these results, it was assumed that TTFD might show these effects against the extrinsic physical invasions through the stabilization of the tissue membrane.