Effects of hexoestrol on the contractility of the isolated, blood-perfused canine papillary muscle and of the guinea-pig ileum.

The effects of hexoestrol were studied on the blood flow and the tension development of the isolated, blood-perfused papillary muscle of the dog, as well as on the contractions of the guinea-pig ileum induced by acetylcholine, histamine or BaCl2. Hexoestrol caused an increase in coronary blood flow and a negative inotropic effect in a dose-dependent manner. High doses of hexoestrol produced a loss of contractility of the papillary muscle without significant alterations of the amplitude and shape of the electrical activity recorded extracellularly. Hexoestrol had a strong non-selective relaxant effect on the guinea-pig ileum and was 10-20 times more potent than papaverine in antagonizing contractions induced by the 3 agonists. These results indicate that hexoestrol probably acts by blocking certain steps in the process by which extracellular and/or superficially bound Ca ions move to the contractile machinery in cardiac and in smooth muscle cells. Thus, it may bear some resemblance to the so-called calcium antagonists.