EFFECT OF PLASMA FROM PREECLAMPTIC SUBJECTS ON CONTRACTIONS OF RAT AORTA

Objective: The study investigated whether plasma from preeclamptic pat ients contains a factor or factors that increase vascular contractilit y or is deficient in factors present in normal pregnancy that diminish the contractility. Methods: Rat aortic rings were incubated for 1 h i n medium containing plasma from normotensive nonpregnant, normotensive pregnant, and preeclamptic subjects. The contractions of de-endotheli alized and intact rings to phenylephrine and potassium chloride were c ompared. Results: The contractile responses to both phenylephrine and potassium chloride by intact rings incubated in plasma from nonpregnan t and preeclamptic women were similar but they were significantly (P < 0.05) greater than those of similar rings incubated in plasma from no rmotensive 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 nor motensive pregnant women such that there was no significant difference between the three groups. De-endothelialization resulted in significa ntly (P < 0.05) reduced response to potassium chloride of rings treate d with plasma from preeclamptic and nonpregnant women but was without significant effect on responses of rings incubated in plasma from norm otensive pregnant women. Conclusions: The results suggest that the pla sma in normal pregnancy contains endothelium-dependent agent(s) that r educe vascular contractility. The agent(s) may be absent or ineffectiv e in the plasma from preeclamptic or nonpregnant subjects. The similar ity of the pattern of effects of plasma to the reports on reactivity o f isolated blood vessels from preeclamptic and normotensive pregnant w omen suggests that the differences in vascular reactivity may be relat ed to the presence of these putative factors.