Tj. Verbeuren et al., EVIDENCE FOR INDUCTION OF NONENDOTHELIAL NO SYNTHASE IN AORTAS OF CHOLESTEROL-FED RABBITS, Journal of cardiovascular pharmacology, 21(5), 1993, pp. 841-845
The aim of our study was to examine the effects of the inhibitor of ni
tric oxide (NO)-synthase, nitro-L-arginine (L-NNA), in atherosclerotic
aortas obtained from cholesterol-fed rabbits. In the atherosclerotic
aortas, L-NNA (100 muM) caused endothelium-independent contractions th
at were not observed in aortas from control rabbits. L-NNA (100 muM) s
ignificantly enhanced the contractile responses to norepinephrine and
5-hydroxytryptamine (5-HT) in atherosclerotic aortas with and without
endothelium; in control aortas, L-NNA only augmented the response to 5
-HT when the endothelium was present. The concentration-dependent incr
eases in the norepinephrine-induced contractions caused by L-NNA (1 to
100 muM) could be reversed by L-arginine (1 mM) both in atherosclerot
ic aortas with and without endothelium. L-NMMA also evoked concentrati
on-dependent augmentations of the norepinephrine-induced contraction;
the effect Of L-NMMA was equipotent to that of L-NNA. Finally, L-NNA (
100 muM) prevented the paradoxical endothelium-independent contraction
to hypoxia in atherosclerotic aortas. These data strongly suggest tha
t nonendothelial NO synthase has been induced in the aortas of the hyp
erlipidemic rabbit.