The Efflux of Substances from Frog Ventricles to Sucrose and to Ringer's Solutions

Abstract

The frog ventricle in sucrose solution contracts for several hours at 25[degree]C, and for as long as 24 hours at 5[degree]C. The possibility that a fraction of the extracellular fluid remains outside of the excitable membrane was examined by measuring the efflux of tracers. The half-time for the efflux to sucrose solution at 25[degree]C of C14 sucrose is about 1 minute, for Na24 is 6. 5 minutes, and for Cl36 is 4 minutes. There is no evidence for the retention of an extracellular Na fraction. The Q10 for Na and Cl efflux is about 1. 3. The half-time for K42 efflux is about 180 minutes; the Q10 is 1. 7. The efflux rates of Na24, Cl36, and K42 to sucrose and to Ringer''s solutions are quite similar. Ca45 efflux is only l/5th as fast to sucrose solution as to Ringer''s; the retention of Ca++ may be important for maintaining excitability in sucrose solution. P32 efflux is 5 times faster to sucrose solution than to Ringer''s solution, and there is a similar increase in the rate of inosine loss to sucrose solution. The Q10 for efflux to sucrose solution is 2. 2 for P32O4 and 2. 4 for inosine. It is suggested that energy metabolism is abnormal in ventricles in sucrose solution and that low temperature prolongs excitability by slowing the metabolic change.