Background. The effect of hydrogen peroxide (H2O2) on vascular tone in the human umbilical artery was investigated to determine the mechanism of vasospasm in preeclampsia. Methods. Helical sections of the umbilical artery were obtained from healthy pregnant women who delivered between the 37th and 39th week of gestation. Changes in the maximal tension induced by prostaglandin F2α (PG F2α) were measured (isometric mechanical activity). Segments were treated with H2O2 alone or H2O2 after pretreatment with a scavenger of hydroxyl radicals (mannitol), an inhibitor of thromboxane synthesis (sodium ozagrel), and an inhibitor of nitric oxide synthesis (L-NG-monomethyl arginine, LNMA), or an inhibitor of prostacyclin synthesis (tranylcypromine, TCP).
Results. Vascular tension was potentiated by H2O2 in a concentration-dependent manner. Pretreatment with mannitol significantly suppressed the vasospastic effect of H2O2. Removal of the endothelium decreased the vascular tension induced by H2O2. Treatment with TCP and LNMA potentiated the vascular tension. Pretreatment with TCP and LNMA reduced the vasospastic action of H2O2, whereas pretreatment with sodium ozagrel did not.
Conclusion. Vascular tension in human umbilical arteries was potentiated by H2O2, and may be mediated by a suppression of the activity of nitric oxide or of prostacyclin. A direct action of H2O2 on vascular smooth muscle may also be involved.