Cloning of inducible nitric oxide synthase in rat vascular smooth muscle cells

We previously showed that interferon(IFN)-gamma inhibited the proliferation of rat vascular smooth muscle cells(VSMC) by generation of nitric oxide(NO) through the induction of an NO synthase(NOS). To identify the NOS in the VSMC at molecular level, we analyzed messenger RNA(mRNA) levels and primary structure of the novel NOS by cDNA cloning with application of polymerase chain reaction(PCR). mRNA of the NOS was induced and the level of induction was significantly increased by IFN-gamma in VSMC within a few hours. The amino acid sequence deduced from the cloned NOS cDNA was distinct from that of the previously reported constitutive types of NOSs, while highly similar to that of macrophage NOS. Cofactor binding regions were highly conserved among these NOSs. These findings show that the NOS is inducible and could regulate the proliferation of VSMC. Besides, this is the first report of cloning of the NOS in VSMC.