Ouabain enhances the lipopolysaccharide-induced nitric oxide production by rat peritoneal macrophages

Incubation of rat peritoneal macrophages with the bacterial product lipopolysaccharide (LPS) caused significant increases in the production of nitrite, a stable endproduct of nitric oxide (NO). Addition of the digitalis-derived glycoside ouabain, which alone is without effect, significantly enhanced the stimulating effects of LPS. The Na+ ionophore monensin was without any effect, while the Ca2+ ionophore A23187, like ouabain, enhanced the effect of LPS. Thus ouabain may enhance the LPS-stimulated NO production in rat peritoneal macrophages via still unknown mechanisms in which Ca2+ ions are most likely involved.