Magnesium deficiency-induced spasms of umbilical vessels: relation to preeclampsia, hypertension, growth retardation.

Isolated umbilical arteries and veins, obtained from normal women at the end of pregnancy, were incubated in krebs-Ringer bicarbonate solution and exposed to magnesium at concentrations ranging from 0 to 9.6 millimoles per liter. The basal tension of the vessels increased when magnesium was withdrawn and decreased when the concentration of magnesium was raised. Absence of magnesium in the medium significantly potentiated the contractile response of the vessels to bradykinin, angiotensin II, serotonin, and prostaglandin F2 alpha. It appears that magnesium deficiency may be responsible for spasms of umbilical and placental vasculature. Our findings may provide a rationale for why magnesium sulfate is an effective therapy in preeclamptic syndromes in pregnant women.