AMINO-ACID HANDLING IN UREMIC RATS - CITRULLINE, A RELIABLE MARKER OFRENAL-INSUFFICIENCY AND PROXIMAL TUBULAR DYSFUNCTION

The kidney is involved in amino acid reabsorption and metabolism; cons equently, in renal insufficiency, these important functions are distur bed, as has been reported in animals and patients. In a first experime ntal series, rats were subjected to degrees of nephrectomy (NX) varyin g between 10% and 90%. Three weeks later, amino acid levels were measu red in plasma to correlate the levels with the degree of NX. The resul ts indicate that in the range of 33% to 74% NX, the plasma concentrati on of only three to four amino acids was modified, whereas in rats wit h 84% NX, the concentration of 11 amino acids was disturbed, compared with sham-operated rats. Citrullinemia was enhanced in uremic rats and correlated with the degree of NX. More interestingly, citrullinemia w as increased in the range of 10% to 33% NX without any changes in urem ia and creatininemia, two well-known markers of uremic states. A secon d experimental series was designed to study the time course of changes in aminoacidemia to find a marker for the onset of renal failure. Rat s were subjected to 36% NX for a period of 1 to 21 days, Uremia and cr eatininemia peaked 24 to 48 hours after NX, and creatinine clearance ( Cl-creat) concomitantly diminished. Unfortunately, these three markers of uremic states returned to control values during the next few days before increasing during the last 2 weeks. In contrast, citrullinemia increased twofold 48 hours after NX and plateaued over the next 20 day s. We conclude that in rats, citrullinemia could be used (1) to detect acute and chronic renal failure, (2) as a specific marker of normal f unction of the proximal tubule, and (3) to estimate the degree of rena l damage. From this study, renal insufficiency might be easily detecte d by measuring citrullinemia. Copyright (C) 1997 by W.B. Saunders Comp any.