IN-VITRO EFFECTS OF LOW-CALCIUM PERITONEAL-DIALYSIS SOLUTIONS ON PERITONEAL MACROPHAGE FUNCTIONS

The use of low-calcium peritoneal dialysis solutions (PDS) for continu ous ambulatory peritoneal dialysis is becoming widely accepted to redu ce the risk of serum hypercalcemia in patients taking calcium salts as phosphate binders. We compared the in vitro effects of low-calcium PD S (1,000 mu mol calcium/L), calcium-free buffer, and buffers with incr easing calcium concentrations (500 to 5,000 mu mol calcium/L) on perit oneal macrophage (PMO) functions. Peritoneal macrophages isolated from 10 continuous ambulatory peritoneal dialysis patients were incubated in the different solutions and tested for phagocytic and killing capac ity, superoxide generation (cytochrome-C reduction and lucigenin-enhan ced chemiluminescence), and the rate of myeloperoxidase-dependent oxid ative metabolism (luminol-enhanced chemiluminescence). All functions o f the PMO incubated in calcium-free buffer were significantly suppress ed compared with the PMO incubated in calcium buffers. No dose-depende nt increase of a single PMO function could be found after incubating t he PMO in calcium buffer with increasing concentrations, Incubation of PMO in otherwise identical PDS containing 1,000, 1,450, or 1,750 mu m ol calcium/L did not result in significantly different PMO functions. Acidic PDS (pH 5.3 to 5.5) suppressed all measured PMO functions as co mpared with their neutralized counterparts (pH 7.4), irrespective of t he calcium concentration. Results of our in vitro study show that low- calcium PDS does not suppress PMO functions any more than standard-cal cium PDS (1,750 mu mol calcium/L) does. (C) 1995 by the National Kidne y Foundation, Inc.