Low-calcium peritoneal dialysis fluid should not impact peritonitis rates in continuous ambulatory peritoneal dialysis.

It has been suggested that reducing the calcium content of peritoneal dialysis fluid (PDF) to 2.5 mEq/L decreases peritoneal macrophage (PMO) function and increases the incidence of peritonitis (especially Staphylococcus epidermidis peritonitis) in continuous ambulatory peritoneal dialysis patients. We studied the uptake and killing of S epidermidis and Escherichia coli by PMOs and peripheral blood leukocytes incubated in control buffer (Hank's balanced salt solution containing 0.1% gelatin [GHBSS]) and PDF containing varying concentrations of calcium (O to 3.5 mEq/L) and magnesium (O to 1.5 mEq/L) using ether diamine tetraacetic acid and ethylenediaminetetraacetic acid chelation, respectively. In addition, interleukin-1-beta-induced interleukin-6 production by human mesothelial cells was measured in the presence of concentrations of calcium 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 to that by PMO incubated in GHBSS with calcium. In contrast, the complement-dependent uptake of E coli was significantly lower in GHBSS devoid of Ca++ (46% +/- 5% v 24% +/- 3%; 0.05 < P < 0.02). No effect on intracellular killing of either microorganism by PMO was observed. The same held true for the phagocytic and killing capacity of polymorphonuclear 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 applied in commercial PDFs, however, phagocytes performed as well as in control buffer. Interleukin-6 production by stimulated human mesothelial cells also required a small amount of Ca++ only, being normal above the 0.1 to 3 mmol/L Ca+ + range tested. Thus, complement- dependent uptake of bacteria by phagocytes is calcium dependent, whereas antibody-dependent uptake of S epidermidis is not. The concentrations of calcium in the current PDFs, however, will not compromise human mesothelial cells and leukocyte functions, and therefore should not impact the peritonitis rate.