Reversible inhibition of cellular respiration by nitric oxide in vascular inflammation

Incubation of rat aortas with endotoxin and interferon-gamma for 24 h resulted in an aortic oxygen consumption that was substantially inhibited and strongly oxygen dependent (37% inhibition at 160 muM O-2 and 62% inhibition at 80 muM O-2 relative to untreated aortas). This respiratory inhibition was reversed by a nitric oxide (NO) scavenger (oxyhemoglobin) or by an inhibitor of inducible NO synthase [N-(3-(aminomethyl) benzyl) acetamide . 2HCl, 1400W], but not by an inhibitor of soluble guanylate cyclase (1H-[1,2,4] oxadiazolo[4,3-a]-quinoxalin-1-one). Addition of 1 mM NO to untreated aortas caused rapid and reversible inhibition of oxygen consumption that was greater at lower oxygen concentrations. Incubation of endothelial cells isolated from rat aortas with endotoxin and interferon-gamma for 24 h resulted in a steady-state NO concentration of similar to0.5 muM and 90% inhibition of cellular oxygen consumption that was immediately reversed by an NO scavenger (oxyhemoglobin). These results suggest that during inflammation and sepsis, tissue respiration may be substantially reduced due to inhibition by NO of cytochrome oxidase.