THE ACTION ON ISOLATED SMOOTH MUSCLE OF KINEKARD, A CARDIOACTIVE FRACTION ISOLATED FROM HUMAN PLASMA

¹ Baker Medical Research Institute, Melbourne, Australia

The action of kinekard on three types of isolated smooth muscle preparations was established and contrasted with that of epinephrine. In isolated segments of rabbit thoracic aorta, a direct constrictor effect of kinekard was demonstrated. The action of kinekard on isolated strips of rabbit ileum and guinea-pig uterus and the ability of several adrenergic antagonists to block this action were studied. In all three isolated smooth muscle preparations the action of kinekard was found to be apparently identical with that of epinephrine. Dose-response curves demonstrated, however, that kinekard and epinephrine are not one and the same substance. Other experiments indicated that kinekard does not act on smooth muscle by liberating endogenous catecholamines. It was concluded that the action of kinekard on smooth muscle may be mediated through the adrenergic receptors.