Effects of glycerol treatment on contractility and transmembrane potentials in cardiac tissue

Abstract

Recordings were made of transmembrane potentials and contractile activity before, during, and after treatment of guinea-pig left atria with Tyrode's solution made hypertonic with 400 m m-glycerol. During treatment with glycerol solution developed tension declined to a steady level while rest tension and transmembrane potentials were unchanged. After return to non-glycerol Tyrode's rest tension increased and developed tension declined further, sometimes to zero resulting in a period of quiescence. With time rest tension declined and developed tension increased, eventually returning to control values. Depolarization of transmembrane rest potentials was shown to accompany the decline of tension after return to non-glycerol Tyrode's. Field stimulation did not prevent these changes. However, if the tissue was placed in 400 m m-sucrose Tyrode's after treatment with 400 m m-glycerol solution, developed tension did not decline at all. In addition, it was shown that increased calcium or magnesium concentration prevents the decline in developed tension as well as depolarization of resting potentials after return to non-glycerol Tyrode's. It was also shown that similar changes in contractile activity occur after glycerol treatment of dog atrial tissue. However, glycerol treatment of frog cardiac tissue has little effect.