NITRIC-OXIDE AND PROSTAGLANDIN SYSTEMS INHIBITION ON THE ISOLATED-PERFUSED HUMAN PLACENTA FROM NORMAL AND PREECLAMPTIC PREGNANCIES

Isolated human placental cotyledons from normal (NG) and preeclamptic gestants (PG) were perfused in vitro, and the effect of N-omega-nitro- L-arginine (LNA, 100 mu M), methylene blue (MB, 50 mu M), and indometh acin (INDO, 10 mu M), on resting perfusion pressure and on the 5-hydro xytryptamine (5-HT)-induced vasoconstriction was established. In the N G, L-NA and MB increased resting perfusion pressure (p < 0.001) and IN DO had no significant effect on resting pressure. In the PG, these age nts did not significantly modify resting perfusion pressure. In the PG , 5-HT (10 nM-1 mu M) caused greater maximal increases in perfusion pr essure than in NG. In the NG, L-NA greatly enhanced the 5-HT-induced p ressure, however INDO attenuated this effect. In the PG, L-NA did not modify significantly the 5-NT-induced response, but INDO reduced this response. These results suggest that basal release of nitric oxide but not of vasodilator prostanoids may contribute to the low resting vasc ular tone in the NG and attenuates the strong vasoconstrictor effect i nduced by 5-HT. Impairment of action of nitric oxide could contribute to the enhanced presser response to 5-HT observed in the PG.