REVERSAL OF IN-VITRO LIPOPOLYSACCHARIDE-INDUCED SUPPRESSION OF CONTRACTION IN RAT AORTA BY N-G-NITRO-ARGININE, DIPHENYLENEIODONIUM AND DI-2-THIENYLIODONIUM

The effects of N-G-nitro-L-arginine (L-NNA), D-NNA, diphenyleneiodoniu m and di-2-thienyliodonium on contraction were studied in endothelium- denuded rat aortic rings incubated for 4 h with lipopolysaccharide (10 mu g ml(-1)) or vehicle. Lipopolysaccharide reduced E(max) and increa sed EC(50) of the phenylephrine (10(-9)-10(-5) M) curve. Addition of D -NNA (4, 6 X 10(-4) M), L-NNA(I, 10 x 10(-6) M) and diphenyleneiodoniu m (1, 3 X 10(-7) M), but not di 2-thienyliodonium (10(-7) M), increase d E(max) and reduced EC(50) of the phenylephrine curve of lipopolysacc haride-incubated but not control rings. Therefore, D-NNA, L-NNA and di phenyleneiodonium, but not di-2-thienyliodonium, inhibit inducible NO synthase in vascular smooth muscles.