Renal responses to amino acids in the sheep fetus.
Woods, Lori L., A. Roger Hohimer, and Lowell E. Davis.
Division of Nephrology, Hypertension, & Clinical Pharmacology
and Department of Obstetrics and Gynecology, Oregon Health Sciences
University, 3181 S.W. Sam Jackson Park Road, Portland, OR 97201
-3098
APStracts 3:0004R, 1996.
Adult animals and humans are known to increase renal blood flow and
glomerular filtration rate (GFR) in response to an acute protein load
or amino acid infusion, however the ontogeny of this phenomenon is
not known. This study was designed to test the hypothesis that
despite normally high baseline amino acid levels in the fetus,
increases in plasma amino acids stimulate increases in GFR before
birth. Eight chronically instrumented fetal sheep (126+/-1 days
gestation) were infused with a mixture of amino acids (0.15 and 0.30
mmol/kg/min) i.v. Plasma [alpha]-amino nitrogen levels increased
significantly from 7.1+/-0.3 to 13.0+/-0.9 and 25.5+/-2.1 mg/dl,
respectively, in response to the two doses, while GFR increased
significantly from 3.2+/-0.4 to 4.0+/-0.5 and 4.6+/-0.5 ml/min.
Arterial pressure did not change. Renal amino acid reabsorption was
significantly increased at all time points during the amino acid
infusion, reaching a value nearly five times that of control by the
last clearance period. Na+ reabsorption was also increased throughout
the infusion. Na+, K+, and Cl- excretions increased significantly
only at the very last time point. These data indicate that the
mechanism(s) responsible for amino acid-induced hyperfiltration are
present and functional even before birth in the sheep. Because
maternal eating patterns and protein intake are known to change
maternal plasma amino acid levels, and amino acids are actively
transported across the placenta, our findings suggest that both acute
and chronic changes in maternal protein intake may alter fetal renal
function.
Received 5 September 1995; accepted in final form 14 December
1995.
APS Manuscript Number R550-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 22 January 96