Key Points
- To quantify and compare plasma renin substrate concentrations in unanaesthetized pregnant ewes and their fetuses during late gestation, evaluating changes after fetal nephrectomy.
- Measured plasma renin substrate (expressed as angiotensin I equivalents) in catheterized, unanaesthetized pregnant ewes and fetal lambs during the last third of gestation.
- Evaluated plasma concentrations longitudinally across early (days 1–5) and late (days 6–14) post-catheterization periods in intact and nephrectomized fetuses.
- Plasma renin substrate at 6–14 days post-catheterization was significantly lower in fetal lambs (212 ± 20 ng/ml) than in paired maternal plasma (350 ± 27 ng/ml).
- Nephrectomized fetal lambs had plasma renin substrate concentrations averaging threefold higher than intact lambs, with similar elevations seen in intact twins immediately post-catheterization.
- Maternal renin substrate was suppressed during the initial 5 days post-surgery unless the ewe carried a nephrectomized fetus.
Structured PICO
PPopulationUnanaesthetized pregnant ewes and their foetal lambs during the last third of gestation
IInterventionCatheterization and foetal nephrectomy (in a subset)
CComparatorMaternal plasma vs foetal plasma; intact vs nephrectomized foetuses
OOutcomeConcentration of renin substrate in plasmasurrogate
Foetal plasma renin substrate concentration is significantly lower than maternal concentration in sheep, suggesting foetal/maternal plasma renin activity ratios understate relative enzyme activity.