EFFECTS OF ULTRAPURE AND NONSTERILE DIALYSATE ON THE INFLAMMATORY RESPONSE DURING IN-VITRO HEMODIALYSIS

Several studies support the hypothesis that bacterial contamination of the dialysate stimulates the inflammatory response to hemodialysis (H D) and increases the long-term morbidity of HD patients; this phenomen on could also be modulated by the nature of the HD membrane. Therefore , this study was designed to compare the effects of non-sterile (NSBD, mean endotoxin content +/- SEM 97 +/- 22 EU/ml) and ultrapure bicarbo nate dialysate (UPBD, sterile and pyrogenfree, obtained by ultrafiltra tion through polyamide) on several aspects of the inflammatory reactio n during in vitro HD. The HD sessions (7 in each experimental group) w ere performed using miniaturized new cuprophane (CU) and polyacrylonit rile (PAN) hollow fiber dialyzers, and closed dialysate and blood circ uits (the latter filled with heparinized blood from healthy donors). P lasma C3aDesarg levels were significantly increased after 15 minutes ( t1) and increased further after three hours (t2) of CU HD, while durin g PAN dialysis they decreased from t0 to t1 and t2; however, no differ ence appeared between experiments with NSBD and UPBD. Granulocyte (PMN ) and monocyte (MNC) expression of LFA-1, Mac-1, and CD45 at the start (t0), t1 and t2 was quantitated by flow cytometry analysis, after sta ining of the cells with specific fluorescinated monoclonal antibodies. In contrast with published data of in vivo HD, LFA-1 was overexpresse d at t1 and peaked at t2, which suggests that the leukocytes expressin g more LFA-1 leave the systemic circulation during in vivo HD. During CU HD, Mac-1 and CD45 on PMN and MNC were significantly increased at t 1, and still more at t2. During PAN HD, Mac-1 and CD45 remained unchan ged at t1, but increased significantly at t2 on PMN as on MNC. Again, no significant difference was found between NSBD and UPBD in LFA-1, Ma c-1 and CD45 expression on PMN and MNC, during both CU and PAN HD. Aft er three hours of dialysis, plasma levels of TNF-alpha, but not of IL- 6, were significantly increased with CU and PAN. Again, no difference appeared when NSBD and UPBD were compared. Moreover, the lack of influ ence of bacterial contamination of the dialysate on TNF-alpha producti on was confirmed when MNC were cultured up to 24 hours after the end o f the HD session. We conclude that complement activation products, eit her in plasma (CU) or those adsorbed on the HD membrane (CU and PAN) p lay the major role in the overexpression of beta 2-integrins and CD45 by PMN and MNC during HD. Also, bacterial products (at the levels that can be found in clinical conditions) do not influence either beta 2-i ntegrin overexpression or TNF-alpha production induced by the dialysis membrane.