Table 1. Effect of aldehyde dehydrogenase or xanthine oxidase inhibition on the GTN NObonome.

Inhibitor	Compartment	NOx, % change	Total nitros(yl)ation, % change
Cyanamide	Plasma	-84 ± 22	-100 ± 40
	RBC	-72 ± 36	-100 ± 44
	Heart	-100 ± 22	-71 ± 40
	Liver	-79 ± 24	-68 ± 33
	Aorta	-97 ± 40	97 ± 42
Allopurinol	Plasma	-12 ± 4	-74 ± 42
	RBC	-26 ± 8	-25 ± 16
	Heart	14 ± 4	103 ± 47
	Liver	-22 ± 6	-27 ± 9
	Aorta	-16 ± 4	32 ± 14

Animals were pretreated with the aldehyde dehydrogenase inhibitor cyanamide (25 mg/kg, i.p.) or the xanthine oxidase inhibitor allopurinol (100 mg/kg, i.p.) for 1 h before i.p. administration of either 10 mg/kg GTN or vehicle. Separate groups of animals were administered one inhibitor or GTN alone. After 15 min, the tissues indicated were processed and analyzed for their contents of nitrite plus nitrate (NO_x) and total nitros(yl)ation products (3, 5, 15). The net GTN-induced metabolite signal in the presence of inhibitor was expressed as a mean percent change relative to the net GTN-induced signal in the absence of inhibitor (means ± SEM of three animals).