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In order to investigate the mechanism by which elevated extracellular calcium ions decrease tetanus tension in frog skeletal muscle, we made mechanical, electrophysiological and photographic measurements on single fibres or small bundles of fibres. Three lines of evidence point to t-tubular conduction failure as the primary mechanism of action of high calcium. They are a decrease in amplitude of the late afterpotential, attenuation or elimination of the notch and hump configuration of the early afterpotential, and the appearance of wavy myofibrils in the axial core of fibres during tetanus. These effects are fully reversible and are shared by other bivalent cations. High calcium concentration causes a change in the time course of the early afterpotential but does not alter the passive cell membrane characteristics, as reflected by the time course of decay of applied hyperpolarizing pulses.

Original publication

DOI

10.1007/bf01574591

Type

Journal

Journal of muscle research and cell motility

Publication Date

06/1987

Volume

8

Pages

229 - 241

Keywords

Muscles, Myofibrils, Animals, Rana temporaria, Calcium, Action Potentials, Muscle Contraction, In Vitro Techniques