Figure 1.

Effects of bepridil on Ca²⁺ activated force in skinned muscle fibres. (A) Submaximal contraction records obtained for the soleus muscle at pCa 6.0 followed by maximal tension elicited by pCa 4.2 solution. The records corresponded to tensions without (No BPD) and with 100 μM or 800 μM BPD. Fast transient peaks on the records and the transient shift of the base line were produced by the changes of the solutions. Upward arrows represented the application of a new solution, while downward arrows indicated withdrawal of the previously applied solution. (B) Tension reinforcement at pCa 6.0 as a function of drug concentration (logarithmic scale). The reinforcement was expressed relative to the tension at pCa 6.0 without BPD. Slow fibres (n=12, open squares) and fast fibres (n=12, filled squares) were obtained from the soleus and tibialis anterior, respectively. s.e.m. were not reported when they merged with the mean points.