Abstract
The possibility of involvement of a Na−Ca exchange mechanism in the contractile responses induced by a reduction of external Na concentration ([Na]0) has been studied in isolated guinea-pig aorta. Low-Na (11.9 mM) solution (Lisubstituted) produced a contraction in ouabain-treated muscles in the presence of phentolamine (10−6 M). The magnitude of the contraction was dependent on the duration of the pretreatment with ouabain (2×10−5 M). Ca-free solution, but not verapamil (10−6 M), abolished the contraction induced by low-Na solution. The muscles were loaded with various amounts of Na by incubating the tissue with ouabain and varying [Na]0 (11.9–148.7 mM) in the absence of Ca. The magnitude of the contractions induced in these muscles by low-Na solution containing Ca (2.5 mM) was dependent on the cellular Na content. Loss of cellular Na into low-Na solution followed a single exponential time course and the rate coefficient of Na-loss in the presence of external Ca was about twice as great as in the absence of Ca. Cellular45Ca uptake in low-Na solution was significantly greater in Na-loaded tissues (pretreated with ouabain for 3 h) than in normal tissues. The45Ca uptake in low-Na solution was not inhibited by verapamil. These results suggest that the contraction induced by low-Na solution is caused by a Ca influx which is dependent on internal Na (a Na−Ca exchange mechanism).
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References
Baker PF (1978) The regulation of intracellular Ca in squid giant axon. In: Scarpa A, Carafoli E (eds) Calcium transport and cell function. The New York Academy Science pp 250–268
Blaustein MP (1977) Sodium ions, calcium ions, blood pressure regulation, and hypertension: a reassessment and a hypothesis. Am J Physiol 232:C165-C173
Brading AF (1978) Calcium-induced increase in membrane permeability in the guinea-pig taenia coli: evidence for involvement of a sodium-calcium exchange mechanism. J Physiol (Lond) 275:65–84
Brading AF, Widdicombe JF (1975) Interaction between sodium and calcium movements in smooth muscle. In: Worcel W, Vassort G (eds) Smooth muscle pharmacology and physiology. INSERM, Paris, pp 235–245
Casteels R, Raeymaekers L (1977) Electrolytes and vascular reactivity. In: Carrier O, Shibata S (eds) Factors influencing vascular reactivity. Igaku Shoin, Tokyo New York, pp 59–77
Chapmann RA, Ellis E (1977) The effects of manganese ions on the contraction of the frog's heart. J Physiol (Lond) 272:331–354
Droogmans G, Casteels R (1979) Sodium and calcium interaction in vascular smooth muscle cells of the rabbit ear artery. J Gen Physiol 74:57–70
Droogmans G, Raeymaekers L, Casteels R (1977) Electro- and pharmacological-coupling in smooth muscle cells of the rabbit ear artery. J Gen Physiol 70:129–148
Fleckenstein A (1977) Specific pharmacology of calcium in myocardium, cardiac pace makers, and vascular smooth muscle. Ann Rev Pharmacol Toxicol 17:149–166
Friedman SM (1974) Lithium substitution and the distribution of sodium in the rat tail artery. Circ Res 34:168–175
Haeusler G, Kuhn H, Thorens S (1980) The effect of tetraethylammonium chloride on calcium fluxes in smooth muscle from rabbit main pulmonary artery. J Physiol (Lond) 303:225–241
Karaki H, Urakawa N (1977) Possible role of endogenous catecholamine in the contractions induced in rabbit aorta by ouabain, sodium depletion and potassium depletion. Eur J Pharmacol 43:65–72
Karaki H, Weiss GB (1979) Alteration in high and low affinity binding of45Ca in rabbit aorta by norepinephrine and potassium after exposure to lanthanum and low temperature. J Pharmacol Exp Ther 211:86–92
Ozaki H, Urakawa N (1979) Na−Ca exchange and tension development in guinea-pig aorta. Naunyn-Schmiedeberg's Arch Pharmacol 309:171–178
Ozaki H, Urakawa N (1980a) Effects of K-free solution on tension development and Na content in vascular smooth muscles isolated from guinea-pig, rat and rabbit. Pflügers Arch (in press)
Ozaki H, Urakawa N (1980b) Effect of vanadate on mechanical responses and Na−K pump in vascular smooth muscle. Eur J Pharmacol 68:339–347
Ozaki H, Karaki H, Urakawa N (1978) Possible role of Na−Ca exchange mechanism in the contractions induced in guinea-pig aorta by potassium free solution and ouabain. Naunyn-Schmiedeberg's Arch Pharmacol 304:203–209
Reuter H, Blaustein MP, Haeusler G (1973) Na−Ca exchange and tension development in arterial smooth muscle. Phil Trans R Soc Lond B 265:87–94
van Breemen C (1975) Transmembrane calcium transport in vascular smooth muscle. In: Bevan JA, Johansson B, Nedergaard OA (eds) Vascular neuroeffector mechanism. S. Karger, Basel pp 67–79
van Breemen C, Aaronson P, Loutenhiser R (1979) Sodium-calcium interactions in mammalian smooth muscle. Pharmacol Rev 30, 167–208
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Ozaki, H., Urakawa, N. Involvement of a Na−Ca exchange mechanism in contraction induced by low-Na solution in isolated guinea-pig aorta. Pflugers Arch. 390, 107–112 (1981). https://doi.org/10.1007/BF00590191
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DOI: https://doi.org/10.1007/BF00590191