Abstract
We have studied the temperature dependence of isometric force, rate of force development and maximal shortening velocity (Vmax) in skinned guinea-pig taenia coli smooth muscle. To eliminate the influence of temperature on activation mechanisms, maximally thiophosphorylated preparations were used. Isometric force in the range 2-35 degrees C was maximal at 22 degrees C with a decrease of 25% at 2 degrees C and 10% at 35 degrees C. Rate of tension development from rigor after photolytic release of ATP increased four-fold between 5 degrees C and 30 degrees C. Vmax increased with a Q10 of about 2 (1.6, range 5-15 degrees C, and 2.2, range 22-30 degrees C). The temperature dependence of the rate of tension development indicates rate-limitation by transitions into force-generating states or by the hydrolysis reaction. The temperature dependence of Vmax reflects effects of temperature on reactions (e.g. the ADP-release) associated with cross-bridge detachment. The small temperature dependence of steady-state force in smooth compared with skeletal muscle suggests differences in the cross-bridge reactions controlling the number of attached force-generating states in the two muscle types.
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