The expression of the inducible nitric oxide synthase messenger RNA on monocytes in severe acute pancreatitis

Background/Aims: Although there have been numerous studies that nitric oxide (NO) is produced in monocytes and macrophages in animal models, it still remains controversial whether NO is produced by human monocytes and macrophages. To clarify whether NO is produced by human monocytes in patients with systemic inflammatory response syndrome (SIRS), we examined the expression of inducible nitric oxide synthase (iNOS) messenger RNA (mRNA) and constitutive nitric oxide synthase (cNOS) mRNA in cultured monocytes derived from severe acute pancreatitis patients complicated with SIRS. Methodology: Monocytes were harvested from peripheral blood of nine severe acute pancreatitis patients with SIRS (group S) and five mild acute pancreatitis patients with no SIRS (group M). Then we examined the expression of iNOS mRNA and cNOS mRNA in cultured monocytes using the reverse transcription PCR (RT-PCR) method. Results: iNOS mRNA was expressed in the cultured monocytes derived from eight of the nine patients in group S, but not in any of the five patients in group M, while cNOS mRNA was not found in cultured monocytes derived from any patient in either group. Conclusions: Although it is still not clear whether NO is produced in human monocytes or not, these findings indicate that iNOS is induced in monocytes in severe acute pancreatitis patients with SIRS, but not in mild pancreatitis patients.