Partial separation of an oxytocic principle from preparations of angiotonin.

A THE name implies, angiotonin is characterized by its action on vascular smooth muscle. This activity is usually assayed from its pressor effect in intact animals. Preparations of angiotonin have also been observed to cause contraction of nonvascular smooth muscle and, on this basis, the pressor activity of angiotonin has been attributed to a direct myotropic action of a single substance' ; this inference has been supported by the destruction of both pressor and myotropic activities by heating angiotonin preparations with 0.5 X XaOH (Luduena) and by the correlation between pressor activity and ability to stimulate guinea-pig ileum found by Picarelli and associates. However, Dekanski found a disassociation between pressor and oxytocic activities of angiotonin samples of varying purity, an observation which suggested that these might contain two active principles; othershave postulated the presence of more than one pressor principle.