Effect of acclimation temperature and pH on contraction of frog sartorius muscle

The effect of acclimation temperature and pH on the isometric twitch and tetanus of sartorius muscle from frog, Rana pipiens, was studied at different experimental temperatures. Seven variables were measured, namely: tension, latent period, time to maximum tension, half-relaxation time, mean rate, maximum rate, and maximum acceleration of tension development. The effect of experimental temperature was similar to that reported in the literature. The effects of acclimation temperature were small and were not compensatory. Different pH's were obtained by varying CO2 in the gas phase, while the HCO3- concentration was kept constant. The main effects of a decrease in pH on the isometric twitch and tetanus were a reduction in tension and rate of tension development and an increase in latent period. A decrease in pH had no effect on the time to maximum tension or the half-relaxation time. Analysis of variance showed that the test temperature had the greatest effect of all three treatments on each variable, the effects of test and acclimation temperature were dependent on neither the test nor the acclimation temperatures. The in vivo relationships between these three treatments are discussed.