Background: Bioincompatible glucose degradation products (GDPs) in fluids for peritoneal dialysis (PD) develop during sterilization and storage. Their biological activity has successfully been monitored through the use of various in vitro methods but their molecular and chemical nature is less well understood. Many GDPs are highly reactive carbonyl compounds. Although some of the identified GDPs are extremely cytotoxic, none of them actually possess cytotoxicity at the concentrations found in PD fluids. Thus, the GDP responsible for the toxicity in PD fluids has not yet been identified. The intention of the present work was to investigate to what extent the unsaturated dicarbonyl compound, 3,4-dideoxyglucosone-3-ene (3,4-DGE) was present in PD fluids, and if it could be responsible for the in vitro effects on L-929 fibroblast cells.
Methods: A commercial preparation of 3,4-DGE and two different liquid chromatography methods were used for the chemical identification and quantification. In vitro bioincompatibility was determined as inhibition of cell growth using the L-929 fibroblast cell line.
Results: 3,4-DGE was present in conventionally manufactured PD fluids at a concentration of 9 to 22 micromol/L. In the newly developed PD fluid, Gambrosol trio, the concentrations were 0.3 to 0.7 micromol/L. When added as synthetic 3,4-DGE to cell growth media at the concentrations measured in conventional PD fluids, the inhibition of cell growth was significantly lower than for that seen with the conventional fluids. However, in the conventional PD fluids the total amount of 3,4-DGE available for toxic reactions most probably was higher than that measured, because 3,4-DGE was freshly recruited from a molecular pool when consumed. The speed of this recruitment was high enough to explain most of the growth inhibition seen for heat-sterilized PD fluids.
Conclusion: 3,4-DGE is present in conventional PD fluids at a concentration between 9 and 22 micromol/L, and is the most biologically active of all GDPs identified to date. Thus, it is the main candidate to be held responsible for the clinical bioincompatibility caused by conventionally manufactured PD fluids.