BACKGROUND: We evaluated whether vessel reactivity to nitric oxide changed after cardiopulmonary bypass, which would play an inportant role in temporary vital organ perfusion.

METHODS: We used the distal aortas of five rats weighing 400-500 g after cardiopulmonary bypass in experimental group. We also used the distal aortas of five rats before cardiopulmonary bypass under sham operation in control group. All cumulative concentration-effect curves were performed in the aortic rings and EC50 and maximal response (Emax) were calculated by using nonlineal logistic regression analysis with the software PRISM (Graphpad, Mountain View, CA).

RESULTS: CPB inhibited acetylcholine induced relaxation in aortic rings and also inhibited sodium nitroprusside (SNP) induced relaxation in ones. It was similar to depression of acetylcholine induced relaxation.

CONCLUSIONS: The depression of aortic rings relaxation after CPB may be associated with attenuated sensitivity of them to NO in rats.