PREECLAMPSIA AND EXPRESSION OF INDUCIBLE NITRIC-OXIDE SYNTHASE MESSENGER-RNA IN UMBILICAL VEIN ENDOTHELIAL-CELLS

Objectives: Vasodilatory nitric oxide (NO) is evidently a factor in pr egnancy physiology and perhaps also in preeclampsia. Human umbilical v ein endothelial cells (HUVECs) express the calcium-dependent NO syntha se (NOS), whereas the scanty data on the expression of the inducible i soform of NOS (iNOS) are discrepant. We have previously shown that HUV ECs can express iNOS and now further characterize the regulation of iN OS induction in freshly isolated HUVECs in vitro. In addition, we stud y whether iNOS mRNA expression is induced in vivo in preeclampsia. Stu dy Design: Freshly isolated HUVECs from normal pregnancies were treate d with proinflammatory cytokines, and inducible NO production was dete cted by measurement of nitrate and nitrite accumulation in the media. The expression of iNOS mRNA in these cells was detected by the reverse transcriptase-polymerase chain reaction. In addition, HUVECs from pre eclamptic (n = 9) and normal (n = 11) pregnancies were lyzed immediate ly after delivery and assayed for iNOS mRNA. Results: The cytokine tre atment of HUVECs led to consistent expression of iNOS mRNA and NO synt hesis. Dexamethasone blunted both the expression of iNOS mRNA and the production of NO, whereas NOS inhibitor N-G-methyl-L-arginine merely s uppressed the release of NO. No iNOS mRNA could be detected under basa l conditions in HUVECs from preeclamptic or control patients. Conclusi ons: HUVECs are able to express iNOS after cytokine-stimulation in vit ro, but this pathway was not activated in preeclampsia.