LOW-CALCIUM PERITONEAL-DIALYSIS FLUID SHOULD NOT IMPACT PERITONITIS RATES IN CONTINUOUS AMBULATORY PERITONEAL-DIALYSIS

been suggested that reducing the calcium content of peritoneal dialysi s fluid (PDF) to 2.5 mEq/L decreases peritoneal macrophage (PMO) funct ion and increases the incidence of peritonitis (especially Staphylococ cus epidermidis peritonitis) in continuous ambulatory peritoneal dialy sis patients. We studied the uptake and killing of S epidermidis and E scherichia coli by PMOs and peripheral blood leukocytes incubated in c ontrol buffer (Hank's balanced salt solution containing 0.1% gelatin [ GHBSS]) and PDF containing varying concentrations of calcium (0 to 3.5 mEq/L) and magnesium (0 to 1.5 mEq/L) using ether diamine tetraacetic acid and ethylenediaminetetraacetic acid chelation, respectively. In addition, interleukin-1 beta-induced interleukin-8 production by human mesothelial cells was measured in the presence of concentrations of c alcium increasing from 0 to 3.0 mmol/L. Fc receptor-mediated uptake of S epidermidis by PMO in the complete absence of Ca++ was comparable t o that by PMO incubated in GHBSS with calcium. In contrast, the comple ment-dependent uptake of E coli was significantly lower in GHBSS devoi d of Ca++ (46% +/- 5% v 24% +/- 3%; 0.05 < P < 0.02). No effect on int racellular killing of either microorganism by PMO was observed. The sa me held true for the phagocytic and killing capacity of polymorphonucl ear granulocytes and monocytes obtained from healthy donors. Using Ca+ (2 to 3.5 mEq/L) and Mg++ (0.5 to 1.5 mEq/L) concentrations as appli ed in commercial PDFs, however, phagocytes performed as well as in con trol buffer. Interleukin-6 production by stimulated human mesothelial cells also required a small amount of Ca++ only, being normal above th e 0.1 to 3 mmol/L Ca++ range tested. Thus, complement-dependent uptake of bacteria by phagocytes is calcium dependent, whereas antibody-depe ndent uptake of S epidermidis is not. The concentrations of calcium in the current PDFs, however, will not compromise human mesothelial cell s and leukocyte functions, and therefore should not impact the periton itis rate. (C) 1996 by the National Kidney Foundation, Inc.