DIFFERENT INDUCTION MECHANISMS OF MESSENGER-RNA FOR INDUCIBLE NITRIC-OXIDE SYNTHASE IN RAT SMOOTH-MUSCLE CELLS IN CULTURE AND IN AORTIC STRIPS

The expression of mRNA for the inducible form of nitric oxide synthase , (iNOS), was studied in rat aortic smooth muscle cells, (SMCs) in cel l culture and in strips of rat aorta by reverse transcriptase coupled to the polymerase chain reaction. iNOS mRNA expression was weak in cul tured SMCs when exposed to either interferon-gamma (IFNgamma) or lipop olysaccharide (LPS), but the combination LPS + IFNgamma enhanced the e xpression. In aortic strips LPS alone induced a pronounced expression, with no further increase by IFNgamma. Cycloheximide potentiated the e xpression of iNOS mRNA in SMCs in culture stimulated with LPS + IFNgam ma but attenuated the response in aortic strips. The results indicate different cellular signaling pathways for the induction of iNOS mRNA b y LPS and/or IFNgamma, in cultured SMCs and in rat aortic strips.