Key result
Reducing calcium concentration substantially decreased unloaded shortening velocity in both frog atrial myocytes and rat ventricular myocardium, with maximal velocities averaging 4.32 and 4.46 muscle lengths/sec.
In skinned cardiac myocytes, calcium concentration directly modulates both isometric tension and unloaded shortening velocity, with species and chamber-specific differences in calcium sensitivity.
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Animal myocyte findings on calcium and velocity warrant no clinical change; leaves open translational relevance to human myocardium.
Hofmann et al. (1992) studied this question. Calcium concentration ([Ca2+]) and caffeine was evaluated on Isometric tension and unloaded shortening velocity. Reducing calcium concentration substantially decreased unloaded shortening velocity in both frog atrial myocytes and rat ventricular myocardium, with maximal velocities averaging 4.32 and 4.46 muscle lengths/sec.
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