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Abstract Replacement of external NaCl by LiCl, choline chloride or sucrose increased tension of rabbit aortic strips and pulmonary arteries despite little change in membrane potential. The Ca content of the aortic strips increased concomitantly with the tension development. A two- to threefold increment in 45Ca influx could be measured when external Na was removed. 45Ca efflux decreased in Na-free, Ca-free solutions where little or no tension developed and increased in Na-free, Ca-containing solution concomitantly with the increase in tension. The possible significance of a Ca transport mechanism in the cell membrane which depends on Na and Ca (Na-Ca exchange) for the regulation of vascular tone is discussed.
Réuter et al. (1973) studied this question.