Magnesium pyrrolidone carboxylate infusion reduces angiotensin II pressor response in pregnant women at risk for hypertension.

OBJECTIVE

Our objective was to investigate the possible restoring action of magnesium on vascular sensitivity to angiotensin II in pregnancy.

STUDY DESIGN

We studied intraplatelet free calcium and the pressor response to angiotensin II in 10 primigravid women (28 to 32 weeks' gestation) at risk for pregnancy induced hypertension on the basis of altered uteroplacental blood velocity waveforms at 20 weeks' gestation, before and after the infusion of 1 gm of magnesium pyrrolidone carboxylate. After the effective pressor dose was achieved or a maximum of 32 ng/kg per minute was reached, we infused 1 gm magnesium pyrrolidone carboxylate and repeated the test. Intraplatelet free calcium was measured by means of fluorescent probes at the beginning and the end of both tests.

RESULTS

Six women were classified as refractory to angiotensin II and four as sensitive (effective pressor dose < 10 ng/kg per minute). After magnesium pyrrolidone carboxylate infusion, the four sensitive women became refractory and the effective pressor dose was significantly enhanced to 32 in all six refractory women. Intracellular free calcium increased significantly during the first angiotensin II infusion, whereas after magnesium pyrrolidone carboxylate administration it did not change significantly.

CONCLUSIONS

Magnesium pyrrolidone carboxylate enhances the vascular refractoriness and intracellular free calcium mediates the pressor response to angiotensin II in pregnancy.