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KMID : 0043319870100020080
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Archives of Pharmacal Research
1987 Volume.10 No. 2 p.80 ~ p.87
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Effect of Sodium on Transmembrane Calcium Movement in the Cat Ileal Longitudinal Muscle
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Rho YJ
Yun I/Kang JS
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Abstract
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To get a better insight into the existence and the role of a Na-Ca exchange mechanism in smooth muscle, the effect of Na substitution with sucrose on tension development, cellular Ca uptake and 45Ca efflux was investigated using isolated cat ileal longitudinal muscle strips. Experimental results were summarized as follows; 1) Exposure of the cat ileal longitudinal muscle to Na-free solution induced a contraction, and the magnitude of the contraction increased after incubation of the muscle strips with ouabain (2 X 10-5M) for 1 hr. 2) Cellular Ca uptake in Na-free solution increased with an increase in Na content of the Na-loading media, and a linear relationship existed between tissue Na content and cellular Ca uptake for 10 min. 3) After tissues were equilibrated in PSS containing 45Ca for 2 hr, cellular Ca uptake decreased with raising the external Na concentration. 4) Removal of medium Na or inhibition of the Na-K pump decreased the rate of 41 Ca efflux. These results strongly suggested that Na substitution increases cellular Ca uptake and decreases the rate of 45Ca efflux via a Na-Ca exchange mechanism.
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