ABSTRACT
N O and superoxide anions react rapidly in vivo, such that the b ioavai labi l i ty o f N O and, as a consequence, N O - m e d i a t e d relaxat ion is attenuated by an increase i n the p roduc t ion o f superoxide anions wi th in the vascular wa l l ( R u b a n y i and Vanhout te , 1986). Enzymes capable o f generating reactive oxygen species wi th in endothelial and smooth muscle cells include e N O S , cyclooxygenase, xanthine oxidase, N A D P H ox id ase and cytochrome P450 enzymes ( W o l i n , 2000). It is difficult to determine the enzymatic source o f reactive oxygen species produced wi th in the vasculature since the available inhibi tors are relatively non-specific.
