Vasoactive effect of sera from preeclamptic patients

Investigated was a bioassay method for measurement of vasoactivity in the serum of preeclamptic patients. Intravital microscopy was used to measure the diameter of the principal arteriole and venule in the gastrolienal mesentery of mice before (VD1) and after (VD2) the intravenous injection of sera from preeclamptic primigravid patients and from preeclamptic primigravid patients after treatment with magnesium sulfate (MgSO4). A vasoactive index (VI) was calculated as VD2/VD1. The VIa (vasoactive index for arteriole) of preeclamptic primigravid patients (0.64 +/- 0.39, mean +/- SD) was significantly different (p less than 0.01) from the VIa of normal primigravid patients (0.91 +/- 0.08) and from the VIa of saline controls (0.99 +/- 0.02). Four of the seven preeclamptic primigravid patients had a duration of signs and symptoms dating from the antepartum period (VIa = 0.53 +/-. 0.42), and for three, the diagnosis was made only in the intrapartum period (VIa = 0.77 +/- 0.38). Sera from the MgSO4-treated preeclamptic patients yielded a VIa of 0.91 +/- 0.14, which was not significantly different from that for either the normal primigravid patients or the saline controls. This VIa value was significantly different (p less than 0.01) from the VIa of the untreated preeclamptic patients. These results suggest that here is a vasoactive substance(s) in the sera of preeclamptic patients which may contribute to their arteriolar vasospasm. The magnitude of vasoactivity appears to be related to the duration and severity of preeclampsia but is masked or disappears after treatment of the patient with MgSO4.