Amino acid loading disrupts whole kidney proximal glomerular-tubular balance in humans.
The effect of amino acid infusion on proximal glomerular-tubular balance (PG-TB) was studied in twelve healthy two-kidney volunteers (2K) and eight uninephrectomized subjects (1K) in similar sodium and protein balance, to provide an extended range of values for renal function.  Amino acid infusion induced a reversible significant increase in GFR: +23 +/- 4 and +18 +/- 3 ml/min/1.73 m2 in 2K and 1K respectively (p < 0.001), but not in absolute proximal reabsorption (APR, calculated as inulin clearance--lithium clearance): +8 +/- 3 and +6 +/- 3 ml/min/1.73 m2 respectively, NS.  Consequently, the fractional increases in APR for both two kidney- and one kidney-subjects (+11 +/- 4 and +14 +/- 6%) were less than the fractional increases in GFR (+20 +/- 3 and 25 +/- 4%), and the effectiveness of PG-TB was significantly decreased to 53.2 and 55.9% (p < 0.001).  Urinary sodium excretion also increased by 116 +/- 24 and 95 +/- 29 mumol/min/1.73 m2 in 2K (p < 0.001) and 1K (p < 0.01) respectively.  Urinary excretion of guanosine 3',5'-cyclic monophosphate (cGMP) simultaneously increased (p < 0.001) by 223 +/- 77 and 350 +/- 135 pmol/min/1.73 m2 during infusion of amino acids in 1K and 2K respectively.  In the whole group of subjects, impairment of the PG-TB was inversely related to the increase in urinary cGMP (p < 0.05).  The results demonstrate that amino acid infusion disrupts proximal glomerular-tubular balance in humans due to non-proportional alterations in glomerular filtration rate and proximal reabsorption, and they suggest that a NO-dependent mechanism may be involved in the disruption.
Tack
I
I
Laboratoire d'Explorations Fonctionnelles Rénales et Métaboliques, Hôpital de Rangueil, CHU de Toulouse, Toulouse, France.
Wilcox
C S
CS
Tran-Van
T
T
Praddaude
F
F
Ader
J L
JL
D000328:Adult; D000596:Amino Acids; D016022:Case-Control Studies; D006152:Cyclic GMP / Q000652:urine; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007668:Kidney / Q000502:physiology; D007687:Kidney Tubules, Proximal / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009318:Natriuresis / Q000502:physiology; D009392:Nephrectomy; D009569:Nitric Oxide / Q000378:metabolism; D010288:Parenteral Nutrition; D012016:Reference Values
D000596:Amino Acids; C037999:azonutril; D009569:Nitric Oxide; D006152:Cyclic GMP