Figure 1.

Impact of blebbistatin on strong binding cross-bridges and the Force-Ca relationship. Panels A and B illustrate the impact of increasing blebbistatin concentration (0 mM circle/solid line, 1 μM squares/dashed line) on the force calcium relationship as a function of the maximally calcium activated force. Blebbistatin induced a similar rightward shift in the Force-Ca relationship at both SL's indicating no SL dependent shift, in contrast to the results observed in DM-cTnC exchanged fibers (c.f. Fig. 3). Blebbistatin induced an equal decline in the maximally activated force production (F_max) at both short (circles) and long (squares) lengths (Panel C) that smoothly declined up to the maximum amount used (1 μM). As with force, the impact of blebbistatin on EC₅₀ (Panel D) was to decrease calcium sensitivity with increasing concentration yet demonstrating no SL dependent shifts in the EC₅₀ as opposed to that observed in DM-cTnC exchanged fibers. Error bars represent the mean ±SE.