Healing Over and Muscle Contraction in Toad Hearts
The influence of temperature, contractures, and Ca2+ on the processes of healing over and muscle contraction was investigated in toad myocardium by simultaneously measuring the size of the injury potential and the twitch tension. Stimulation with single pulses and electrically induced contractures of short duration (2-3 seconds) markedly increased the rate of healing, and epinephrine (10-6 g/ml) increased the effectiveness of stimulation. Other results supported the view that the healing process was largely dependent on temperature, since at 15°C or 10°C the rate of healing over was greatly reduced. The effect of temperature was probably related to a reduction in Ca2+ uptake. A possible change in junctional conductance produced by low temperature probably was not the reason for the decrease in rate of healing. Strontium, which replaces Ca2+ in the mechanical process, was also a good substitute for Ca2+ in healing over. The results stress the parallelism between the healing process and the contractile process in heart muscle.
- Received April 4, 1972.
- Accepted July 6, 1972.
- © 1972 American Heart Association, Inc.