Effects of Pregnancy and Magnesium Sulfate Infusion on Blood Pressure and Plasma Catecholamines

ABSTRACT

Magnesium sulfate (MgSO₄) infusion often lowers blood pressure, but the responsible mechanisms are not clear. Since catecholamines play a major role in blood pressure regulation, we studied the effects of MgSO₄ infusion on blood pressure, pulse rate, and plasma catecholamines in late pregnant and in nonpregnant New Zealand white rabbits. Pregnancy was associated with higher levels of dopamine (P < 0.01) and epi-nephrine (P < 0.001). MgSO₄ treatment decreased mean arterial pressure (P < 0.001), increased pulse rate (P < 0.01), decreased dopamine (P < 0.01) and decreased epinephrine (P < 0.001). No significant effect on norepinephrine levels was noted, and there was no evidence that the effect of MgSO₄ treatment was influenced by pregnancy. Further investigation is needed to clarify the role of catecholamines in mediating the effects of pregnancy and MgSO₄ treatment on blood pressure regulation.