'Double toxicity' of glycine solution in the mouse

To study whether glycine, which may contribute to the symptoms of the transurethral resection syndrome promotes death in a mouse model and whether a modification of the glycine concentration offers a better chance of survival.

Mortality was determined in 120 mice after an intravenous infusion of increasing volumes and concentrations of glycine solution. The animals were divided into groups of 10 and given 150, 180, 200 or 220 mL/kg body weight of 1.1, 1.5 or 2.2% glycine solution. As a control, 220 mL/kg of a 5% mannitol solution was given to 12 mice.

After receiving an isosmotic (2.2%) glycine solution 70% of the animals died, while the overall death rate for 1.5% glycine was only 20%. When 1.1% glycine was used, the mortality was 10% after infusion of 150 and 180 mL/kg and 80% after infusion of > or = 200 mL/kg. Logistic regression analysis showed that the outcome for the two highest glycine concentrations was directly related to the dose of glycine and not to the water load. Of 12 mice receiving the isosmotic 5% mannitol solution, three died.

A 1.5% glycine solution offered the best chance of survival. The mortality was governed both by the glycine dose (2.2 and 1.5%) and the tendency of the solution to produce overhydration of the cells (1.1%). Glycine toxicity was most important when small volumes were infused.