Electrical and mechanical activity in heart tissue of flounder and rainbow trout during acidosis.

1. Twitch force and voltage across the sarcolemma were measured in heart tissue of flounder and rainbow trout. 2. For the trout heart, hypercapnia was followed by a loss of force and an action potential prolongation. 3. This was also observed for the flounder heart, but only initially. 4. About 5 min after the onset of hypercapnia, an increase in force and a shortening of the action potential occurred in the flounder heart. 5. After about 30 min of hypercapnia a decrease in force and a prolongation of the action potential slowly appeared. 6. These results can be interpreted in terms of a species-dependent effect of acidosis on the cellular Ca2+ handling and the influence of intracellular Ca2+ on the action potential.