Induction of nitric oxide synthase in human mammary arteries in vitro

This study investigated whether human mammary arteries express an inducible nitric oxide (NO) synthase and, if so, what its effects are on vascular tone. In human mammary artery pre-contracted with phenylephrine there was a gradual time-dependent loss of tone over an 8 h period. L-Arginine and lipopolysaccharide enhanced the rate but not the magnitude of this loss in tone, whereas NG-nitro-L-arginine, NG-monomethyl-L-arginine, dexamethasone, and polymyxin B inhibited these effects. These findings indicate that incubation of human mammary artery with lipopolysaccharide resulted in the expression of an inducible NO synthase. The induction of this enzyme in human vessels may be important in the pathogenesis of septic shock.