Differential expression of inducible nitric oxide synthase gene by alveolar and peritoneal macrophages in lipopolysaccharide-hyporesponsive C3H/HeJ mice

In lipopolysaccharide (LPS)-hyporesponsive C3H/HeJ mice, alveolar macrophages (AM phi) produce much more tumour necrosis factor-alpha than peritoneal macrophages (PM phi) when stimulated with LPS (10 mu g/ml), but the induction of inducible nitric oxide synthase (iNOS) gene expression and production of nitric oxide (NO) in AM phi are not found. In the present study, we determined the induction of iNOS gene expression, using semi-quantitative reverse transcription-polymerase chain reaction, and the release of NO in AM phi and PM phi from C3H/HeJ and C3H/HeN mice. The results showed the induction of iNOS mRNA accumulation in a dose-dependent manner by LPS alone or in combination with interferon-gamma in both macrophages. The effects of the stimuli on iNOS gene expression and NO production were significantly higher in AM phi than in the PM phi of C3H/HeJ mice. The response of macrophages from C3H/HeN mice was similar to those from C3H/HeJ mice, but the difference of iNOS gene expression between AM phi and PM phi in C3H/HeN mice was not as striking as in C3H/HeJ mice. The results show that the iNOS gene expression and NO production were activated differently in AM phi and PM phi and suggest that the functional properties of macrophages isolated from distinct origins are different.