Nitric oxide production following in vitro stimulation of ovine pulmonary alveolar macrophages

Production of inducible nitric oxide (NO) as measured by nitrite in supernatant from ovine pulmonary alveolar macrophage (PAM) cultures was assessed following stimulation of PAM with live cells and supernatants from Corynebacterium pseudotuberculosis and Pasteurella haemolytica cultures; purified bacterial lipopolysaccharide derived from both Esherichia coli and Pasteurella haemolytica alone and in combination with interferon-gamma or lymphocyte conditioned medium; or ovine lentivirus. PAM cultured ex vivo with no further stimulation for 24 h, 48 h or 72 h, produced low concentrations of NO that was not substantially increased following co-culture by the various additives. Assessment of NO production in PAM cultures containing P. haemolytica or supernatant from P. haemolytica cultures was complicated by production of high levels of nitrite in the bacterial cultures. Species differences in inducible NO production may affect the efficacy of clearance of bacterial infections and be responsible for inter-host differences in disease expression following infection by intracellular pathogens.