Expression of inducible nitric oxide synthase in human cultured endometrial stromal cells

The aim of the present study was to investigate the expression of mRNA and protein for inducible nitric oxide synthase (iNOS) in human cultured endometrial stromal cells. The endometrial stromal cells were cultured in the absence or the presence of cytokines such as interleukin (IL)-1 beta and interferon (IFN)-gamma, which are inherently detectable in the endometrium. Nested reverse transcription-polymerase chain reaction detected iNOS mRNA in stromal cells cultured without cytokines. Northern blot analysis failed to detect iNOS mRNA in stromal cells cultured for 9 h in the absence of cytokines or in the presence of IL-1 beta (10-100 ng/ml) or IFN-gamma (10-1000 U/ml) alone, but could detect iNOS mRNA cultured in combinations of IL-1 beta and IFN-gamma. The concentrations of iNOS mRNA were increased as early as 3 h after the addition of the cytokine combination and persisted for up to 36 h, Western blot analysis demonstrated iNOS protein in stromal cells cultured for 12 h with combined IL-1 beta and IFN-gamma. These results raise the possibility that nitric oxide locally synthesized by iNOS may be involved in the control of endometrial functions.