Transferrin induces nitric oxide synthase mRNA in rat cultured aortic smooth muscle cells

Incubation with holo-transferrin, but not apo-transferrin, induced the nitrite accumulation in the culture medium of rat aortic smooth muscle cells concentration- and time-dependently, which occurred after a lag period of 6 hours. The accumulation of nitrite was inhibited by N omega-nitro-L-arginine and cycloheximide, but not by calmidazolium. Ferric or ferrous iron had no effect on the accumulation. In reverse transcription-coupled polymerase chain reaction analysis, one amplified fragment (580 bp) corresponding to the inducible form of nitric oxide synthase (iNOS) mRNA was expressed after incubation with holo-transferrin for 10 hours. These results suggest that holo-transferrin activates expression of iNOS mRNA in rat aortic smooth muscle cells accompanied by nitric oxide accumulation via a pathway dependent on L-arginine in the culture medium.