Events Occurring in the Region of the Threshold for Potassium-Induced Contractures of Frog Skeletal Muscle. Changes in Elasticity and Oxygen Consumption
- 1 March 1972
- journal article
- Published by Canadian Science Publishing in Canadian Journal of Physiology and Pharmacology
- Vol. 50 (3) , 179-187
- https://doi.org/10.1139/y72-028
Abstract
Small bundles of fibers of the semitendinosus of Rana pipiens were subjected to rapid stretches in normal Ringer solution and solutions containing potassium in concentrations just below the mechanical threshold for tension development. The resistance to stretch (R.T.S.) increased with increasing [K+]0. The increase in R.T.S. was dependent on the duration of exposure; the maximum occurred after about 30 s while longer exposures led to a decrease in the R.T.S. The maximum increase in the R.T.S. varied from two to six times the normal R.T.S. The increase in the R.T.S was hyperbolically related to [K+]0. An attempt was made to correlate the mechanical activation and the increase in respiration in muscles exposed to elevated [K+]0 (Solandt effect) by continuously measuring the oxygen consumption [Formula: see text] of toe muscles. Following exposure to an elevated [K+]0 just below the mechanical threshold, the [Formula: see text] started to increase after about 30 s and took 2–3 min to reach a new steady level. The results suggest that: (a) a low level of activation of the contractile elements occurs just below the mechanical threshold for tension development, (b) the excitation–contraction coupling process of frog striated muscle is one of continuous change, i.e. without a sharply defined threshold, and (c) the Solandt effect is probably the expression of a continuous relaxation-type process.Keywords
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