Figure 2. Effect of 10 mM BDM on force and ATPase activity in the absence (continuous line) and presence (dashed line) of 30 mM P_i.

A, mean results (±s.e.m.) obtained from 10 mechanically skinned bundles of myofibrils. B, results obtained from 4 Triton X-100-treated skinned fibres. The intercepts at zero force in A reflect the SR ATPase activity as a fraction of the total ATPase activity without added P_i. The intercepts at zero force in B were not significantly different from zero, indicating that SR ATPase activity was completely abolished by the Triton X-100 treatment.