Length and PKA Dependence of Force Generation and Loaded Shortening in Porcine Cardiac Myocytes

Figure 3

Sarcomere length dependence of the rate constant of force redevelopment (𝑘_tr). (a) Slow time-based recordings of sarcomere length and force obtained using an IonOptix SarLen system during a slack restretch maneuver during submaximal Ca²⁺ activation. (b) Sarcomere length-dependence of 𝑘_tr for rat slow-twitch skeletal muscle fibers, rat cardiac myocytes, and pig cardiac myocytes. Although pig cardiac myocyte 𝑘_tr was much slower at all sarcomere lengths compared to rat cardiac myocytes, both pig and rat cardiac cell preparations showed that 𝑘_tr increased at short sarcomere lengths despite reductions in force implicating that sarcomere length overrides the Ca²⁺ activation dependence of 𝑘_tr.

(a)

(b)