NECROSIS AND APOPTOSIS OF POLYMORPHONUCLEAR CELLS EXPOSED TO PERITONEAL-DIALYSIS FLUIDS IN-VITRO

Conventional peritoneal dialysis (PD) fluids are known to inhibit poly morphonuclear cells (PMN) phagocytosis, oxidative burst and enzyme rel ease. However, the relative contributions of apoptosis and/or necrosis to this dysfunction have not been examined. We investigated the effec ts of osmolality, glucose concentration and heat-sterilization of PD f luids on necrosis and apoptosis of PMN. Polymorphonuclear cells were i solated from 8 healthy volunteers and exposed to different PD fluids f or four hours. PMN were then double-stained with Hoechst 33342 and pro pidium iodide to study the proportion of viable, apoptotic and necroti c cells. Transmission electron microscopy (TEM) was performed to confi rm the results obtained with flow cytometry. The fluids studied were c onventionally heat-sterilized 1.5% Dianeal(R) (1.5%D), conventionally heat-sterilized 4.25% Dianeal(R) (4.25%D), 1.5%D in which the osmolali ty was increased to that of 4.25%D by adding mannitol (1.5%D + M), a f ilter-sterilized version of 4.25%D (4.25%D-F) and a 1.1% amino acid PD fluid (AA) (Nutrineal(R) PD4). All PD fluids had their pH equilibrate d (pH = 7.4) by the addition of sodium bicarbonate. Compared to PMN ex posed to culture medium, a significantly higher proportion of necrosis was observed in PMN exposed to 1.5%D (P = 0.04). The 4.25%D induced g reater necrosis than 1.5%D (P = 0.001), and the 4.25%D also induced si gnificantly more necrosis (P = 0.002) compared to 4.25%D-F. These data suggest that the consequences of heat-sterilization, rather than high glucose concentration are responsible for the necrosis observed. Inde ed, the proportion of necrotic PMN with 4.25%D-F was not significantly different from 1.5%D. The 1.5%D + M and AA induced significantly more apoptosis compared to 1.5%D (P = 0.006 and P < 0.05, respectively), s uggesting that apoptosis can be induced by the high osmolality of PD f luids. However, 1.5%D+/-M also induced significantly more apoptosis (P = 0.007) compared to 4.25%D-F. This suggests that the apoptosis effec t is specific for the osmolyte present in PD fluids, and that mannitol and amino acids induce more apoptosis than glucose. In summary. the d ifferent non-physiological components of conventional PD fluids evalua ted in this study had a differential effect on PMN survival. Heat ster ilization of high glucose-containing PD fluids was associated predomin antly with necrosis of PMN, and high osmolality with apoptosis.