Biocompatibility of bicarbonate buffered peritoneal dialysis fluids: influence on mesothelial cell and neutrophil function.

The present study compares the effects of lactate and bicarbonate buffered PDF on human neutrophil (PMN) and human peritoneal mesothelial cell (HPMC) viability and function. Acute exposure of PMN to lactate buffered PDF at pH 5.5 (CAPD 2, 1.5% and CAPD 3, 4.25% glucose) resulted in significant reductions in cellular ATP levels, the phagocytosis of serum treated zymosan (STZ) and respiratory burst activation (CL). Exposure of PMN to bicarbonate buffered PDF (BIC 20, 1.5% glucose and BIC 30, 4.25% glucose both at pH 7.2) had no significant effect on cell viability or the CL response. Phagocytosis was, however, depressed significantly more following exposure to BIC 30 than BIC 20. PMN cellular ATP levels and phagocytosis were significantly better in cells exposed to BIC 30 than to CAPD 3 at pH 7.4 (P = 0.043 for both). Pre-exposure of HPMC to CAPD 2, CAPD 3 or BIC 30 for 30 minutes resulted in a significant reduction in cellular ATP content compared to control medium. Pre-exposure to BIC 20 did not result in a reduction in HPMC ATP levels. HPMC synthesis of IL-6 was unaffected by 15 or 30 minutes pre-exposure to BIC 20 or BIC 30, in contrast pre-exposure to CAPD 2 or CAPD 3 for 15 or 30 minutes resulted in a significant reduction in stimulated IL-6 synthesis (24.5 +/- 3.01 and 32.3 +/- 5.0 vs. 43.9 +/- 10 pg/microgram cell protein in M199, N = 6; P = 0.02). Neutralization of the pH of CAPD 2 and CAPD 3 resulted in normalization of HPMC IL-6 secretion. Analysis of IL-6 mRNA expression in control, BIC 20 and 30 pre-treated HPMC subsequently stimulated with IL-1 beta revealed no differences in the expression of the IL-6 specific 465 base pair transcripts. The improved cellular function in bicarbonate buffered PDF indicates potentially improved host defence status and preservation of the peritoneal membrane in CAPD patients.