Control of Aldosterone in Normal and Hypertensive Pregnancy: Effects of Metoclopramide

Abstract

To test whether factors other than angiotensin II (AII) are important in the control of aldosterone during pregnancy, we examined the inhibitory effects of dopamine upon aldosterone release during normal pregnancy in women with pregnancy-induced hypertension (PIH) and in normal age-matched nonpregnant women, using the dopamine antagonist metoclopramide.

Plasma renin (PRC), plasma aldosterone (PAC), and serum Cortisol concentrations were measured before and 30 minutes after intravenous metoclopramide in 6 non-pregnant women during both phases of their menstrual cycle, 6 women taking oral contraceptive pills (OCPs) during both halves of their menstrual cycle, 6 normal third-trimester primigravidas and 9 women with PIH. AII were sodium replete and eating an adlibitum diet. Six pregnant and 6 non-pregnant women served as controls and had the same measurements before and after 2 ml intravenous saline instead of metoclopramide. Baseline PRC, PAC and Cortisol were higher in normal pregnant than non-pregnant women and PRC was reduced significantly from values for normal pregnancy in those with PIH. Serum Cortisol was elevated significantly in women taking OCPs compared with other non-pregnant women (P <0.05). PAC increased following metoclopramide in every subject, but PRC and Cortisol remained unchanged. PAC, PRC or Cortisol were not altered significantly over the same time period in control subjects. Although the percentage increment in PAC following metoclopramide was greater in women with PIH than in normal pregnant women (P <0.05), absolute changes were not significantly different between these two groups. Our findings demonstrate that dopamine exerts considerable inhibitory influence upon aldosterone release in both non-pregnant and pregnant women despite markedly elevated aldosterone concentration in pregnancy. This effect is apparent in both normotensive pregnant women and in those with PIH.