[Positive inotropic effect of amiloride and inhibition of Na+/Ca2+ exchange: dependence on temperature].
Na+/Ca2+ exchange plays a fundamental role in the regulation of intracellular Ca2+ levels and thus myocardial contractility. The influence of temperature variations on Na+/Ca2+ exchange activity in bovine heart sarcolemmal vesicles has been studied. Furthermore, the temperature dependence of positive inotropic response induced by amiloride, an inhibitor of Na+/Ca2+ exchange activity, has been investigated in isolated guinea-pig left atria driven at 1 Hz. Our results indicate that cooling from 37 degrees to 20 degrees C inhibits Na+/Ca2+ exchange activity in sarcolemmal vesicles, whereas does not change the extent of Na+/Ca2+ exchange inhibition by amiloride. In addition, the positive inotropic effect induced by amiloride in guinea-pig left atria decreases and eventually disappears when temperature is progressively reduced from 35 degrees to 23 degrees C. A possible relationship between the decrease in Na+/Ca2+ exchange activity induced by cooling and the temperature dependence of positive inotropic effect of amiloride is discussed.
Debetto
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Dipartimento di Farmacologia, Università degli Studi, Padova.
Bova
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Cannas
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Cargnelli
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Luciani
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D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002316:Cardiotonic Agents / Q000494:pharmacology*; D002417:Cattle; D066298:In Vitro Techniques; D007474:Ion Exchange; D009206:Myocardium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013696:Temperature
D002316:Cardiotonic Agents; D000584:Amiloride; D012964:Sodium; D002118:Calcium
Effetto inotropo positivo dell'amiloride e inibizione dello scambio Na+/Ca2+: dipendenza dalla temperatura.