EFFECT OF 2-CHAMBERED BICARBONATE LACTATE-BUFFERED PERITONEAL-DIALYSIS FLUIDS ON PERIPHERAL-BLOOD MONONUCLEAR CELL AND POLYMORPHONUCLEAR CELL-FUNCTION IN-VITRO

Low pH, high osmolality, increasing glucose concentration, and glucose degradation products (GDP) formed during heat sterilization of conven tional peritoneal dialysis (PD) fluids have been shown to have a detri mental effect on cells involved in peritoneal host defense. The two-ch ambered PD fluid bag in which glucose at pH similar to 3 is separated from a bicarbonate (25 mmol/L)-lactate (15 mmol/L) buffer during heat sterilization permits PD fluids with lower GDP to be delivered to the patient at neutral pH. To establish the possible benefit of two-chambe red bag PD fluids on peripheral blood mononuclear cell (PBMC) and poly morphonuclear (PMN) cell function, we compared conventional 1.5% Diane al (1.5%D) with 1.5% two-chambered bag bicarbonate-lactate (1.5%D-B), and conventional 4.25% Dianeal (4.25%D) with 4.25% two-chambered bag b icarbonate-lactate (4.25%D-B). Furthermore, to study the effect of the sterilization process on PBMC and PMN function, we compared filter-st erilized 4.25%D (4.25%D-F) with 4.25%D and 4.25%D-B. PBMC were harvest ed by Ficoll-Hypaque separation, and 2.5 x 10(6) cells in RPMI were in cubated with an equal volume of the test fluids for 4 hours, pelleted, and resuspended in RPMI containing 10 ng endotoxin for a further 20 h ours. Tumor necrosis factor alpha (TNF alpha) production by endotoxin- stimulated PBMC was not significantly different (P = 0.10) between 1.5 %D-B and 1.5%D, but was significantly higher (P = 0.01) with 4.25%D-B compared with 4.25%D. PBMC exposed to filter-sterilized fluid (4.25%D- F) showed significantly higher endotoxin-stimulated TNF alpha producti on compared with 4.25%D (P = 0.02), but was not significantly differen t from 4.25%D-B (P = 0.40). PMN were harvested by Ficoll-Hypaque separ ation and 10 x 10(6) cells incubated with test fluids for 30 minutes. After incubation, phagocytosis (phagocytosis index) was determined by the uptake of C-14-labeled Staphylococcus aureus, oxidative burst by r eduction of ferricytochrome C to ferrocytochrome C on stimulation with PMA, and enzyme release by measurement of endotoxin-stimulated bacter icidal/permeability increasing protein (BPI). Bicarbonate-lactate two- chambered fluids of similar osmolality and glucose concentration confe rred a significant improvement in phagocytosis (P = 0.02 for 1.5%D-B a nd P < 0.001 for 4.25%D-B). Oxidative burst and BPI release were signi ficantly higher in 4.25%D-B compared with 4.25%D (P < 0.001). Filter-s terilized 4.25%D-F conferred a significant improvement in phagocytosis and oxidative burst compared with 4.25%D (P < 0.001) or 4.25%D-B (P < 0.001). Furthermore, conventional 4.25%D was associated with signific antly lower BPI release compared with 4.25%D-F (P = 0.01). GDP's aceta ldehyde and 5-HMF were analyzed in 4.25%D-B, 4.25%D, and 4.25%D-F. Ace taldehyde was below the lower limit (0.79 ppm) of the standard curve i n 4.25%D-B and 4.25%D-F fluids but was detected (3.76 to 5.12 ppm) in all of the 4.25%D fluids. Relative levels of 5-HMF in the 4.25%D-B (0. 032 to 0.041 Abs @ 284 nm) and 4.25%D (0.031 to 0.036 Abs @ 284 nm) we re similar. The lowest levels (0.001 Abs @ 284 nm) were observed in th e filter-sterilized 4.25%D-F. The beneficial effects of two-chambered bicarbonate lactate-buffered PD fluids on PBMC and PMN function are pr obably related to reduction of GDP from heat sterilization of glucose in a separate chamber at a lower pH. This improvement in biocompatibil ity could have a beneficial affect on peritoneal defenses. (C) 1997 by the National Kidney Foundation, Inc.