Lack of iNOS expression and NO formation by mononuclear phagocytes from hamsters upon stimulation in vitro

In previous investigations, we demonstrated that hamster alveolar macrophages failed to induce the iNOS and produce NO upon stimulation in vitro. The subject of this study was to examine whether the lack of the iNOS pathway in hamster mononuclear phagocytes is tissue-specific. We investigated iNOS expression and NO production in isolated hamster (Lak:LVG(SYR)BR) monocytes (MO), pleural macrophages (PLM), and peritoneal macrophages (PM) in comparison to isolated rat (Crl:CD®(SN)BR) cells. NO release was measured as nitrite with the Griess reaction upon stimulation with lipopolysaccharide (LPS) and/or interferon-γ (INF-γ). The expression of the iNOS protein was detected with western blot-technique and iNOS mRNA was analyzed by RT-PCR. As expected, rat MO, PLM, and PM released NO upon stimulation with LPS and/or IFN-γ. However, hamster cells were not able to generate detectable amounts of NO. Expression of the iNOS protein and iNOS mRNA was only detected in rat, but not in hamster MO, PLM, and PM. Our data indicate that NO may not belong to the effector system of hamster mononuclear phagocytes.