Key result
Nitrate ion increases calcium influx and tension during muscle contraction, while caffeine causes calcium release without membrane depolarization.
This basic science study demonstrates that calcium release and influx are key mediators of muscle contraction and contracture, influenced by agents like nitrate and caffeine.
These in vitro observations should not change clinical practice; leaves open effects on human cardiac contractility.
The movements of calcium in muscle have been followed during contraction and contracture to test the hypothesis that the release of calcium from the surface of the muscle membrane during stimulation initiates the contractile mechanism. Nitrate ion increases the calcium influx during a single twitch and during potassium contracture, and also increases the tension developed. The increased entry of calcium during a potassium contracture is transient and not sustained as is the contracture. Caffeine, which brings about a contracture without depolarization of the membrane and despite the absence of calcium from the medium, causes calcium to be released from the muscle.
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Brooks et al. (1961) studied Muscle contraction. Nitrate ion and caffeine was evaluated on Calcium movements and tension during contraction and contracture. Nitrate ion increases calcium influx and tension during muscle contraction, while caffeine causes calcium release without membrane depolarization.
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