[Nature of the sensitizing influence of urea on the effects of catecholamines].

Tests conducted on aortic strips of rabbits, portal veins and musculus rectococcygeus in rats showed the urea to nonspecifically increase the effects of norepinephrine at the expense of a greater calcium permeability of membranes and, possibly, also at the expense of a higher sensitivity of the myosin adenosine-triphosphatase to the action of calcium ions without affecting the function of adrenoreceptors.