Renin activation in normal and hypertensive human pregnancy

Severe pregnancy-associated hypertension (P-AH, preeclampsia) is characterised by lowered plasma renin activity and plasma renin concentration, despite concomitant plasma volume contraction. Measurement of total (active + trypsin activatable) and active renin concentrations in peripheral blood of 13 women with P-AH revealed low active levels, but total renin concentrations (193 ± 61 ng/ml A1) which were not significantly different from those of 20 normotensive pregnant women (174 ± 54 ng/ml A1). Women with more severe P-AH as assessed by the presence of proteinuria (± 500 mg per day) had the lowest levels of active renin concentration (3.9 ± 1.3 ng/ml A1, vs 10 ± 4.5 in the normals, p < 0.01). This may represent failure of secretion of active renin or failure of activation of inactive renin.