IN VITRO EFFECT OF SALICYLATE ON AMINO ACID ACCUMULATION BY KIDNEY CORTEX SLICES

Depletion of plasma glycine and effect of glycine by mouth on salicylate metabolism during aspirin overdose

1. The metabolism of aspirin was investigated in 45 patients who had taken self-administered overdose of aspirin and were treated with fluids only, glycine, N-glycylglycine by mouth, or by sodium bicarbonate i.v. 2. The major metabolite recovered in the urine of patients treated with oral fluids, glycine or N-glycylglycine was salicyluric acid, which accounted for means of 51%, 47% and 38% of the total, respectively; salicylic acid comprised 19%, 29% and 29%. In contrast, salicylic acid (42%) was the major urinary metabolite recovered from patients treated with sodium bicarbonate. 3. Plasma glycine concentrations in healthy volunteers who had taken no aspirin remained constant through the day and were not affected by a therapeutic dose (500 mg) of aspirin. Plasma glycine was consistently lower in patients with aspirin overdose than in these healthy volunteers, suggesting depletion of available glycine. 4. Orally administered glycine and N-glycylglycine increased plasma glycine. While the fraction of total salicylate recovered as salicyluric acid was not altered, the maximum rate of excretion of salicyluric acid was higher in patients who received glycine than in the control group; there was no significant difference in the maximum rate of excretion of salicyluric acid between the group that received glycine and the group that received N-glycylglycine. 5. The data suggest that exogenous glycine increases the rate of formation of salicyluric acid in salicylate overdose.

The effect of diamide on amino acid transport by rat renal cortex slices

Diamide directly added to renal cortical slices inhibits the uptake of amino acids. Steady-state kinetic analysis indicates an inhibition of alpha-amino acid influx without effect on efflux. The effect could be reversed by addition of pyruvate to the incubation medium. Although there was a good correlation of the transport effect of diamide with its ability to decrease cellular reduced glutathione concentration, there did not appear to be a necessary connection between them. This was shown by the fact that renal cortical slices stored at 4 degrees C have no alteration in amino acid uptake despite the fact that GSH concentration is as low as that seen with diamide. Diamide was shown to have a direct effect on the uptake of glycine by isolated renal brush border membrane vesicles.

The effects of salicylate on the concentrations of amino-acids in mouse tissues

The concentrations of amino-acids in chopped preparations of mouse liver incubated with 0 to 20 mM salicylate were measured. The changes, observed with salicylate concentrations of 10 mM and above, were increased concentrations of aspartate, glutamine, tyrosine and ornithine and decreased concentrations of glutamate and γ-aminobutyrate. The effects of the intraperitoneal injection of salicylate, in doses ranging from 75 to 600 mg/kg body weight, on the amino-acid concentrations in mouse blood, kidney, liver and brain were studied. With a dose of 600 mg/kg, the amino-acid concentrations were decreased in the blood (except glutamate and aspartate which increased) and in the kidney, were increased in the liver (except glutamine, glutamate, glycine and alanine which decreased) and were unchanged in the brain (except alanine, valine and leucine which decreased and γ-aminobutyrate which increased). These changes may result from a combination of an inhibitory effect of salicylate on the renal tubular transport of the amino-acids and intracellular actions of the drug on aminotransferase and other enzyme activities.

Inhibitory effect of salicylate on the incorporation of L-(U-14C)leucine into the protein of rat tissue preparations in vitro

1. The inhibitory effect of salicylate, in concentrations ranging from 0.1 to 20mm, on the incorporation of radioactivity from l-[U-(14)C]leucine into the protein of isolated rat diaphragm muscle and of cell-free systems from rat liver was studied. 2. The lowest salicylate concentrations producing significant inhibitions of amino acid incorporation were as follows: isolated rat diaphragm, 0.1mm; rat-liver mitochondrial-microsomal system, 0.1mm; rat-liver microsomal system, 0.3mm. 3. Salicylate concentrations of 2.5mm and above were found to inhibit creatine-kinase activity in vitro.