Bicarbonate/lactate dialysis solution improves in vivo function of peritoneal host defense in rats

Objective:To assess the in vivo peritoneal inflammatory reaction in rats di alyzed with neutral, bicarbonate-lactate-buffered dialysis fluid. Methods: Chronic peritoneal dialysis was performed for 4 weeks in Wistar ra ts with two solutions: (1) 40 mmol/L lactate-buffered fluid, pH 5.2, with a glucose concentration of 2.27 g/dL (Lac); and, (2) 15 mmol/L lactate and 2 5 mmol/L bicarbonate-buffered fluid, pH 7.0 - 7.5, with a glucose concentra tion of 2.27 g/dL (Bic-Lac). After 4 weeks, two peritoneal equilibration te sts (PET 1 and PET 2) were performed in all animals with each respective so lution. PET 1 was done with test solutions alone, whereas, on a subsequent day, PET 2 was performed with test solutions supplemented with endotoxin [l ipopolysaccharide (LPS)] to induce peritonitis. Results: During PET 1 no consistent differences were detected in peritoneal permeability between the Lac and Bic-Lac groups. Total dialysate cell coun t in the Bic-Lac animals was lower than in rats treated with Lac fluid: tha t is, at 8 hours, the respective counts were 1858 +/- 524 cells/mu L versus 2785 +/- 1162 cells/mu L (p < 0.01). Dialysate from animals dialyzed with Bic-Lac contained more macrophages (at 4 hours: 53.6% +/- 35.8% versus 35.8 % +/- 8.8%, p < 0.001) and fewer neutrophils (at 4 hours: 3.6% +/- 1.8% ver sus 15.4% +/- 6.1%, p < 0.001) as compared to those dialyzed with the Lac s olution. Concentration of nitrites in 8-hour dwell dialysate samples from B ic-Lac rats was lower than that in the Lac group (0.98 +/- 0.28 mu mol/mL v ersus 2.32 +/- 0.87 mu mol/mL, p < 0.002), but cytokine levels in the dialy sates were comparable. During PET 2, the increase in peritoneal permeabilit y resulting from the LPS-induced inflammatory response was similar for both test solutions. Dialysate cell count was higher in the Lac group versus th e Bic-Lac group (at 8 hours: 8789 +/- 4862 cells/mu L versus 3961 +/- 581 c ells/mu L, p < 0.001), contained more neutrophils (at 8 hours: 80.0% +/- 11 .3% versus 54.8% +/- 4.4%, p < 0.001) and fewer macrophages (at 8 hours: 6. 8% +/- 5.6% versus 21.2% +/- 3.3%, p < 0.05). During peritonitis, we found a higher overall dialysate concentration of both tumor necrosis factor (TNF alpha: +53%, p < 0.05) and of interferon gamma (IFN-gamma +303%, p < 0.02) , in the Bic-Lac group than in the Lac group. Conclusions: A lower dialysate cell count, higher percentage of macrophages , and lower percentage of neutrophils in dialysate suggest that Bic-Lac flu id induces a diminished nonspecific inflammatory response of the peritoneal cavity during dialysis. However, after in vivo stimulation, peritoneal cel ls from animals dialyzed with Bic-Lac solution possess an augmented ability to produce inflammatory cytokines.