Inducible L-arginine-dependent nitric oxide synthase activity in bovine bone marrow-derived macrophages

In rodent macrophages, cytokines or bacterial constituents induce a Ca(2+)-independent nitric oxide (NO) synthase which plays a key role in antimicrobial and tumoricidal activity. Firm evidence for expression of a similar enzyme in other mammals has been lacking. Here we show that bovine bone marrow-derived macrophages produce nitrite in an L-arginine-dependent manner upon stimulation with heat-killed gram-positive or gram-negative bacteria. NO2- production was markedly diminished by arginase, and by the arginine analogue, NG-monomethyl-L-arginine. Bacteria-induced NO2- production was enhanced by concomittant exposure to interferon-gamma, tumor necrosis factor-alpha or both combined, although these cytokines alone (in the absence of bacteria) induced little NO2-. This is one of the first demonstrations of NO2- production by non-rodent macrophages.