EFFECTS OF NITRIC-OXIDE DONORS IN-VITRO ON THE ARACHIDONIC ACID-INDUCED PLATELET-RELEASE REACTION AND PLATELET CYCLIC-GMP CONCENTRATION IN PREECLAMPSIA

1. Platelet activation in vivo occurs in healthy pregnancy and is more pronounced in pre-eclampsia. 2. This study has investigated: (i) the inhibitory potency of the nitric oxide donors 3-morpholino-sydnonimine and sodium nitroprusside, on the platelet release reaction in vitro in non-pregnant, healthy pregnant and pre-ectamptic women; (ii) the concentration of cyclic GMP during incubation of washed platelets with sodium nitroprusside in a separate group of non-pregnant, healthy pregnant and preeclamptic women. 3. The half-maximal inhibitory concentration of sodium nitroprusside, in the presence of a phosphodiesterase inhibitor, for inhibition of the platelet release reaction was lower in the pre-eclamptic subjects than in the non-pregnant subjects (P<0.05). 4. Several of the pre-eclamptic women were studied again postnatally. The half-maximal inhibitory concentrations of sodium nitroprusside and 3-morpholinosydnonimine were higher in the postnatal than in the antenatal sample (P<0.02). 5. Peak platelet cyclic GMP responses to sodium nitroprusside were significantly higher in the preeclamptic women than in the healthy pregnant and non-pregnant women. 6. These results suggest that platelets are more sensitive to the inhibitory effects of nitric oxide donors in pre-eclampsia.