Fig. 3.

Myosin II inhibitor blebbistatin (Bleb) reduced both active (KCl-induced) and passive (stress-relaxation in a Ca²⁺-free solution) tension values. Examples of a tension tracings showing that there was full recovery of tension produced following a single stretch-release (SS-R) applied at the pseudo steady state (30 min) of a KCl-induced contraction (tension at data point f₂ was equal to tension at data point f₁; A). B: Bleb relaxed a KCl-induced contraction when applied at the pseudo steady-state period of tension maintenance (tension at data point f₂ was less than tension at data point f₁). C: degree of tension held during a passive stress-relaxation in a tissue incubated in a Ca²⁺-free solution was reduced by a SS-R applied at the pseudo steady-state period of stress-relaxation (tension at data point f₂ was less than tension at data point f₁). D: Bleb relaxed the degree of tension held during a passive stress-relaxation in a tissue incubated in a Ca²⁺-free solution when applied at the pseudo steady-state period of stress-relaxation (tension at data point f₂ was less than tension at data point f₁). To induce stress-relaxation, tissues were stretched rapidly from 120 to 180% L_s (Stretch, C and D). A, inset: zoomed tension tracing taken from 29.5 to 30.5 min. Control tissues for the tests shown in A and B were contracted for 60 min with KCl, and control tissues for the tests shown in C and D were stress-relaxed in a Ca²⁺-free solution for 60 min (data not shown but results are summarized in Fig 4).