In vitro pharmacological study of femoral artery vascular reactivity after inferior canine hindlimb ischemia/reperfusion: effects of in vivo nitric oxide blocker infusion.

The aim of the investigation was to study the possible effects of in vivo infusion of nitric oxide (NO) blockers upon the in vitro endothelium-dependent femoral reactivity. The experimental model tested herein was the inferior canine hindlimb global ischemia induced by infrarenal abdominal aortic cross-clamping followed by reperfusion. The NO blockers employed in the tests were N(G)-nitro-l-arginine methyl ester (L-NAME), aminoguanidine (AMG), and methylene blue (MB), which were infused immediately after the anesthesia induction. The research protocol was standardized in two main experimental groups, control and ischemia/reperfusion (I/R) injury, randomized in eight subgroups including controls and NO blockers. The femoral artery vascular reactivity was studied in vitro with the aid of a setup consisting of eight organ chambers, where segments of 4-5 mm were suspended and connected to force transducers in the presence of indomethacin to block the cyclooxygenase pathway. The NO-release pathway was evaluated by using specific pharmacological agonists in the in vitro experiments. The L-NAME in vivo infusion led to in vitro endothelium dysfunction in both groups and was associated with high mortality in the animals submitted to I/R. AMG and MB, two clinically used drugs, did not cause in vitro endothelium dysfunction in either of the two groups, which gives evidence that these drugs are not deleterious in the milieu of I/R injury. Nitrite/nitrate plasma levels were not significant except for the L-NAME groups, which presented significant NO decrease.