Potentiating effect of NH 4Cl on vasoconstriction in rat aorta

Abstract

The effect on the vasocontractile response of pretreatment with NH 4Cl at a concentration (10 mM) that made almost no change in the resting tension was investigated using aortic strips from rats. NH 4Cl pretreatment for 10 min significantly potentiated strip contractions induced by KCl (≦ 30 mM), BAY K 8644 (0.1 μ M) and phenylephrine (0.01 μ M). This potentiating action of NH 4Cl was eliminated in presence of nifedipine (1 μ M). KCl (14.7 mM)-stimulated 45Ca uptake in rat aorta was significantly potentiated by pretreatment with NH 4Cl (10 mM) for 10 min, but this NH 4Cl effect was also eliminated in the presence of nifedipine. These results suggest that NH 4Cl potentiates contractions induced by KCl and agonists in rat aorta by facilitating calcium influx through the nifedipine-sensitive calcium channel.