Myonemal contraction of Spirostomum. III. The thermal dependence of contraction, relaxation and excitation-contraction coupling.

A microphotometric technique that displays rapid length changes of Spirostomum has been used to follow the variation with temperature of these kinetic parameters of myonemal contraction: contraction rate, relaxation rate and stimulus duration at threshold. In each case the exponential form of the relationship indicated that the gross rate constant might be equated with the limiting rate constant, k, of a driving chemical reaction, and from standard expressions of chemical kinetics the change in activation free energy appropriate to this reaction has been computed.