[Influence of variations of Ca++ on responses of segments of the isolated coronary artery to acetylcholine].

The effect of external calcium concentration on the Ach-induced contraction of coronary arteries was studied in vitro. It resulted that the effect of Ach was enhanced by the increase, or reduced by the decrease of calcium concentration. It is concluded that, as it was known for the intestinal smooth muscle, also for the smooth muscle of the coronary arteries, the contractile effect of Ach is dependent on the calcium of the medium.