Effect of plasma from preeclamptic subjects on contractions of rat aorta

Objective: The study investigated whether plasma from preeclamptic patients contains a factor or factors that increase vascular contractility or is deficient in factors present in normal pregnancy that diminish the contractility. Methods: Rat aortic rings were incubated for 1 h in medium containing plasma from normotensive nonpregnant, normotensive pregnant, and preeclamptic subjects. The contractions of de-endothelialized and intact rings to phenylephrine and potassium chloride were compared. Results: The contractile responses to both phenylephrine and potassium chloride by intact rings incubated in plasma from nonpregnant and preeclamptic women were similar but they were significantly (P < 0.05) greater than those of similar rings incubated in plasma from normotensive pregnant women. De-endothelialization did not significantly alter the response to phenylephrine of rings treated with plasma from nonpregnant and preeclamptic women, but it did cause significant (P < 0.05) increase in the responses of rings treated with plasma from normotensive pregnant women such that there was no significant difference between the three groups. De-endothelialization resulted in significantly (P < 0.05) reduced response to potassium chloride of rings treated with plasma from preeclamptic and nonpregnant women but was without significant effect on responses of rings incubated in plasma from normotensive pregnant women. Conclusions: The results suggest that the plasma in normal pregnancy contains endothelium-dependent agent(s) that reduce vascular contractility. The agent(s) may be absent or ineffective in the plasma from preeclamptic or nonpregnant subjects. The similarity of the pattern of effects of plasma to the reports on reactivity of isolated blood vessels from preeclamptic and normoten-sive pregnant women suggests that the differences in vascular reactivity may be related to the presence of these putative factors.