TENSION STIFFNESS RATIO OF SKINNED RAT SKELETAL-MUSCLE FIBER TYPES ATVARIOUS TEMPERATURES/

It is well known that shortening velocity and maximal tension of muscl e preparations are strongly dependent on experimental temperature. Con versely, studies about temperature effects on muscle fibre stiffness a re scarce. In the present study, we measured tension and stiffness of maximally Ca2+ activated skinned rat skeletal muscle fibres of differe nt types over a wide temperature range. Ail fibre types exhibited a si milar tension/stiffness ratio at each experimental temperature. This r atio increased almost linearly from 6 to 18 nm when the temperature wa s raised from 6 to 34 degrees C. Our results are discussed in the ligh t of the drastic discrepancies reported for the amount of compliance i nside and outside the attached myosin cross-bridges of activated muscl e fibres (Ford er al. 1981, Huxley el al. 1994, Kojima el al. 1994, Wa kabayashi er al. 1994, Higuchi et al. 1995). The relation between thes e compliances had been deduced from various experimental approaches ex ecuted at different temperatures. The large temperature sensitivity of the tension/stiffness ratio found in this study provides evidence for the assumption that the compliance outside the cross-bridges increase s with rising temperature, This view would reconcile the contrasting r esults reported for the relation of compliances inside and outside the attached cross-bridges.