Differential effects of amino acids on the isolated perfused rat kidney

1. The direct effects of individual amino acids, including glycine (a neutral amino acid), L-glutamic acid (an acidic amino acid), L-leucine (a neutral, branched-chain amino acid) and L-arginine (a basic amino acid), on renal function were compared with a mixed amino acid solution by using the isolated rat kidney perfused with a physiological saline solution containing 6.7% (w/v) albumin and a basal level of 2 mmol/l mixed amino acids. 2. In a control series, the renal perfusate flow was stable but the glomerular filtration rate, as measured by [14C]inulin clearance, declined with time. A stable glomerular filtration rate could be obtained by increasing the basal perfusate amino acid concentration to 14 mmol/l. 3. The addition of 6 mmol/l mixed amino acids produced a sustained increase in renal perfusate flow and an increase in [14C]inulin clearance, reversing its time-dependent fall. Sodium reabsorption was enhanced, but, unlike the control series, no increase in fractional albumin excretion was obtained. 4. Renal perfusate flow was increased by glycine (6 mmol/l), L-arginine hydrochloride (6 mmol/l) and sodium glutamate (6 mmol/l) but remained unaffected by L-leucine. The vasodilatation induced by L-arginine hydrochloride and sodium glutamate was not sustained. 5. The time-dependent fall in [14C]inulin clearance was prevented by glycine, L-arginine and glutamic acid, but not by L-leucine. L-Arginine hydrochloride, like the mixed amino acid solution, produced a significant increase in [14C]inulin clearance.(ABSTRACT TRUNCATED AT 250 WORDS)