NITRIC-OXIDE SYNTHASE - MESSENGER-RNA EXPRESSION OF DIFFERENT ISOFORMS IN HUMAN MONOCYTES MACROPHAGES/

To detect mRNA expression of nitric oxide synthase (NOS) isoforms in h uman monocytes/macrophages reverse transcription polymerase chain reac tion (RT-PCR) was used. mRNA was isolated from stimulated or unstimula ted monocytes/macrophages and RT-PCR was performed using oligonucleoti de primers derived from mRNA sequences of either human endothelial con stitutive (c) or human hepatocyte inducible (i) NOS. RT-PCR of mRNA is olated from resting monocytes and macrophages resulted in the amplific ation of a cNOS specific mRNA fragment. When the cells were stimulated with lipopolysaccharide (LPS)/interferon-gamma (IFN-gamma) prior to m RNA extraction, RT-PCR yielded an iNOS-specific amplification product. Whereas the activation of both cell types was accompanied by expressi on of iNOS mRNA, the cNOS signal seemed to be diminished upon immunost imulation. Not only in purified human monocytes but also in the human monocytoid cell lines MonoMac 6, THP-1, and U937 cNOS mRNA was detecte d. The data clearly demonstrate the presence of iNOS and cNOS mRNA in human monocytes/macrophages and provide the necessary tools to investi gate the regulation of NO synthesis in these cell populations.