Key result
Laserflash photolysis of caged-ATP in guinea pig cardiac tissue revealed a steady-state ATP hydrolysis rate of 0.4 s-1 in the presence of calcium, with a tension increase half-time of 0.3 s.
The rate-limiting step of ATPase in isometric cardiac fibers is slower and subsequent to the nucleotide hydrolysis step, likely involving an actomyosin-ADP complex.
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Supports actomyosin-ADP as rate-limiter in cardiac fibers; leaves open translation to human contractility or therapies.
Barsotti et al. (1988) studied Guinea pig cardiac muscle physiology. Laserflash photolysis of caged-ATP vs. Absence of calcium ions was evaluated on Kinetics of ATP hydrolysis and tension responses. Laserflash photolysis of caged-ATP in guinea pig cardiac tissue revealed a steady-state ATP hydrolysis rate of 0.4 s-1 in the presence of calcium, with a tension increase half-time of 0.3 s.
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