Effects of conventional and new peritoneal dialysis fluids on leukocyte recruitment in the rat peritoneal membrane

Peritonitis remains an important cause of morbidity and technique failure in peritoneal dialysis (PD). Conventional peritoneal dialysate fluids (PDF) inhibit peritoneal leukocyte function in vitro and may thus adversely affect the immune response to peritonitis. New PDF have been designed with neutral pH, low glucose degradation product (GDP) contents, and bicarbonate as buffer. The present intravital microscopy study examined the effects of conventional and new PDF on leukocyte behavior in the peritoneal microcirculation of Wistar rats. The visceral peritoneum was superfused by a control solution (EBSS), a conventional (CAPD), or a new bicarbonate-buffered PDF with neutral pH and low GDP content (CAPD BicaVera). In addition, spent conventional and new PDF were tested. The number of rolling, adhering, and extravasated leukocytes and leukocyte rolling velocity were assessed at different time intervals after exposure to lipopolysaccharide (LPS) or cell-free supernatants of coagulase-negative staphylococci (CNS-CFS). Exposure to LPS or CNS-CFS dissolved in EBSS dramatically increased the number of rolling, adhering and extravasated leukocytes and decreased leukocyte rolling velocity. Superfusion by CAPD, abolished the LPS- or CNS-CFS-induced leukocyte recruitment, whereas CAPD BicaVera had significantly fewer depressant effect. Spent PDF affected the leukocyte response in a similar way as fresh PDF. High lactate concentrations, GDP, and hypertonicity appeared to be mainly responsible for the inhibition of leukocyte recruitment. In conclusion, conventional PDF abolish in vivo leukocyte recruitment in reponse to potent inflammatory stimuli. Bicarbonate-buffered pH-neutral PDF with low GDP contents have fewer depressant effects and may therefore contribute to a better preservation of peritoneal host defense.