A quantitative study to assess synergistic interactions between urotensin II and angiotensin II.

Interaction between the vasoactive peptides, urotensin II and angiotensin II, could have important implications in various disease states. We examined this interaction using isolated rat aortic rings with intact adventitia and endothelium. The fixed-ratio combination we tested produced effect levels significantly greater than predicted by additivity. Thus, the interaction was synergistic, and this is illustrated in a response surface plot that shows the predicted additive effect for all possible combinations.