| dc.description.abstract |
Renal and cardiovascular immaturity has been linked with poor outcomes in thepremature human newborn. Despite extensive study in the fetus, thecontribution of the renin-angiotensin system to renal and cardiovascularfunction in the premature newborn has not been well characterized. To evaluatethe angiotensin II contribution to preterm newborn renal and cardiovascularfunctions, preterm (120-day) and near-term (136-day) lambs were Caesareandelivered and ventilated. One hour following delivery, animals were randomizedto receive angiotensin II receptor-blockade (saralasin; 20 gkg<emph type="7">-1 min<emph type="7">-1) or saline(CON). Prior to blockade, mean SEM values for urine flow(U<emph type="8">Flow), urinary sodium excretion(U<emph type="8">NaV), and fractional excretion of sodium (FENa) weresimilar in all groups. Angiotensin II receptor-blockade decreasedU<emph type="8">flow, U<emph type="8">NaV and FENa in the120-day group with no changes in the 136-day animals. No changes in meanarterial pressure, or plasma angiotensin II, aldosterone, and renin activitylevels were noted at either gestational age. Conclusions:(1) angiotensin II contributes to the regulation ofrenal function in 120-day preterm lambs without changing blood pressure and(2) angiotensin II-mediated feedback inhibition of reninrelease is uncoupled in preterm newborns. |
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