Effect of endogenous vasoconstrictors on maternal intramyometrial and fetal stem villous arteries in pre-eclampsia.

The contractile responses to various endogenous vasoactive agents were investigated in isolated human uteroplacental arteries from normotensive (NT) patients and patients with pre-eclampsia (PE) undergoing caesarian section. Tissue samples were obtained from the uterine incision and from macroscopically normal cotyledons. Vascular ring preparations of intramyometrial and stem villous arteries (length 1.0-1.3 mm, outer diameter 400-600 microns) were dissected and mounted in organ baths and isometric tension was recorded. Concentration-response relationships for vasopressin (VP), oxytocin (OX), angiotensin II (Ang II), noradrenaline (NA), 5-hydroxytryptamine (5-HT), prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E2 (PGE2) were assessed. For each compound, the mean maximum contractile effect (Emax) and the drug concentration producing half-maximal response (EC50) were determined. In intramyometrial arteries from NT and PE patients, VP, Ang II, NA, 5-HT and PGF2 alpha induced contraction while OX and PGE2 produced weak or no responses. Preparations from PE patients showed higher Emax values, while no differences in EC50 were found between the two groups. In fetal stem villous arteries, Ang II, 5-HT, PGF2 alpha and PGE2 induced contractions, while VP, NA and OX produced weak responses. No differences in Emax or EC50 values were found between the fetal vessels of PE and NT patients. No qualitative differences were demonstrated in response to the agents tested between the vessels (fetal and maternal) from NT women at term and PE patients. However, the results may reflect quantitative differences, suggesting increased contractility of maternal uteroplacental arteries from women with PE.