1. Pre-eclampsia is characterized by reduced plasma active renin conce
ntration and renal prostacyclin production. The aim of this study was
to determine whether the plasma active renin concentration could be st
imulated in women with pre-eclampsia by intravenous frusemide, which s
timulates renin acutely through a prostacyclin-mediated mechanism. 2.
Plasma active renin concentration, plasma aldosterone concentration, h
aematocrit and urinary sodium, creatinine and 6-keto-prostaglandin F-1
alpha were measured before (0) and 15, 30 and 60 min after intravenou
s frusemide in 10 non-pregnant women, 10 normal pregnant women and nin
e women with preeclampsia. Six normal pregnant and six non-pregnant wo
men underwent the same measurements after injection of 2ml of saline t
o control for effects of time and posture. 3. Baseline plasma active r
enin concentration (but not plasma aldosterone concentration) was lowe
r in pre-eclamptic women [4.0 (1.7-6.2) pmol of angiotensin I h(-1) ml
(-1); median (interquartile range)] than in normal pregnant women [6.7
(5.3-12.2) pmol of angiotensin I h(-1) ml(-1)] (P < 0.05). Baseline u
rinary 6-keto-prostaglandin F-1 alpha/creatinine ratio, urinary sodium
excretion and fractional sodium excretion did not differ between norm
al pregnant and pre-eclamptic women. 4. After frusemide, plasma active
renin concentration rose significantly in non-pregnant (P = 0.002) an
d normal pregnant (P = 0.008) women, but not in women with pre-eclamps
ia. Individual results showed stimulation in all non-pregnant and norm
al pregnant women but in only six out of nine pre-eclamptic women, sig
nificantly fewer than in normal pregnancy (P < 0.05). The overall magn
itude of the response of plasma active renin concentration to frusemid
e was blunted significantly in pre-eclamptic compared with normal preg
nant women (P = 0.022).5. Absolute and fractional sodium excretion and
haematocrit rose significantly in all groups and the magnitude of cha
nge did not differ among groups for any of these parameters. The urina
ry 6-ketoprostaglandin F-1 alpha/creatinine ratio increased significan
tly only in non-pregnant women (P = 0.01), with variable individual re
sponses in normal and hypertensive pregnant women. 6. This study shows
that normal pregnant women exhibit natriuresis and stimulation of pla
sma renin after frusemide similar to that of non-pregnant women. Howev
er, pre-eclamptic women, as a group, have impaired renin stimulation a
fter frusemide but a similar natriuresis to that of normal pregnant wo
men. The mechanisms of these changes are unclear but are consistent wi
th the notion of 'exhausted' renal renin in some women with pre-eclamp
sia.