Increased Contribution of l -Arginine–Nitric Oxide Pathway in Aorta of Mice Lacking the Gene for Vimentin

Experiments were designed to investigate endothelial function in the aorta of mice lacking the gene for the cytoskeleton protein vimentin (vim -/- ). Rings with and without endothelium from wild-type (vim +/+ ), heterozygous (vim +/- ), and homozygous (vim -/- ) mice were suspended in organ chambers to record of changes in isometric tension. During phenylephrine contraction, acetylcholine evoked comparable endothelium-dependent relaxations in the three groups. In the presence of Nomega-nitro-L-arginine, acetylcholine caused endothelium-dependent contractions, which were greater in vim -/- than in vim +/+ and vim +/- aortas. Indomethacin did not affect relaxation to acetylcholine in vim +/+ or in vim +/-, but it significantly increased the maximal response in vim -/- (67 +/- 7 vs. 102 +/- 4%). Response to acetylcholine in vim -/- aortas was not affected by cyclooxygenase type 2 inhibitor NS-398, the thromboxane receptor antagonist SQ-29,548, or superoxide dismutase. Relaxations to sodium nitroprusside were not different between vim +/+ and vim -/- mice and were not affected by cyclooxygenase inhibition. Cyclic guanosine monophosphate levels, which were increased to a comparable level by acetylcholine in vim +/+ and vim -/-, were augmented by indomethacin in vim -/- aortas but not in vim +/+ aortas. Expression of endothelial nitric oxide synthase was not different between vim +/+ and vim -/- preparations. These results suggest that despite comparable endothelium-dependent responses to acetylcholine, endothelial cells from vim -/- mice release a cyclooxygenase product that compensates the augmented contribution of nitric oxide.