Calcium‐activated force responses in fast‐ and slow‐twitch skinned muscle fibres of the rat at different temperatures.

Abstract

1. Force responses from mechanically skinned fibres of rat skeletal muscles (extensor digitorum longus and soleus) were measured at different temperatures in the range 3‐35 degrees C following sudden changes in Ca2+ concentration in the preparations. 2. At all temperatures there were characteristic differences between the slow‐ and fast‐twitch muscle fibres with respect to the relative steady‐state force‐[Ca2+] relation: such as a lower [Ca2+] threshold for activation and a less steep force‐pCa curve in slow‐twitch muscle fibres. 3. At 3‐5 degrees C the force changes in both types of muscle fibres lagged considerably behind the estimated changes in [Ca2+] within the preparations and this ena..