The Expression of Inducible Nitric Oxide Synthase in the Human Fallopian Tube During the Menstrual Cycle and in Ectopic Pregnancy

Objective: To investigate the production of inducible nitric oxide synthase (iNOS) in the fallopian tube (FT) during the menstrual cycle and whether epithelia from FTs bearing an ectopic pregnancy differ from healthy tubes in iNOS expression.

Design: Prospective study.

Setting: Academic unit of reproductive and developmental medicine.

Patient(s): Fallopian tubes from the different stages of the menstrual cycle (n=12), FTs bearing an ectopic pregnancy (n=15), and FTs from pseudopregnant women (n=6) were collected.

Intervention(s): In the pseudopregnant group, patients were injected with hCG in the days leading up to hysterectomy. Samples were processed for immunohistochemistry staining and quantitative reverse transcriptase polymerase chain reaction.

Main Outcome Measure(s): To compare iNOS protein and messenger RNA expression between the different groups.

Result(s): This is the first report on cyclicity in iNOS production by human fallopian tube during the menstrual cycle. The intensity of expression of iNOS was higher in the ectopic pregnancy group compared with the pseudopregnant group (P<0.05).

Conclusion(s): The cyclicity in iNOS expression by the tube suggests its involvement in fertilization and early embryonic development. Pathologic generation of nitric oxide through increase iNOS production may decrease tubal ciliary beats and smooth muscle contractions and thus affect embryo transport, which may consequently result in ectopic pregnancy.