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 cell culture and in strips of rat aorta by reverse transcriptase coupled to the polymerase chain reaction. iNOS mRNA expression was weak in cultured SMCs when exposed to either interferon-gamma (IFNgamma) or lipopolysaccharide (LPS), but the combination LPS + IFNgamma enhanced the expression. In aortic strips LPS alone induced a pronounced expression, with no further increase by IFNgamma. Cycloheximide potentiated the expression of iNOS mRNA in SMCs in culture stimulated with LPS + IFNgamma but attenuated the response in aortic strips. The results indicate different cellular signaling pathways for the induction of iNOS mRNA by LPS and/or IFNgamma, in cultured SMCs and in rat aortic strips.