Peritoneal fibrosis remains one of the major causes of dropout in continuous ambulatory peritoneal dialysis (CAPD), because it reduces ultrafiltration capacity. Since studies in vitro have demonstrated that cytoplasmic Ca2+ regulates the proliferation of most cell lines and the release of cytokines from immune cells, we evaluated in 8 uremic patients at the start of CAPD and in 4 control patients the effects in vitro of different peritoneal dialysis solution Ca concentrations (1, 1.25, 1.75, and 2 mmol/L) on peritoneal fibroblast (PF) proliferation, peritoneal macrophages (PM phi), and peritoneal lymphocyte (PLy) release of interleukin-1 (II-1) and interferon-gamma (IFN-gamma) (cytokines which are known to induce PF proliferation), and cytoplasmic Ca2+ concentration in PF, PM phi, and PLy. Results showed that in both the uremic and control patients, increasing the dose of Ca2+ in the medium induced a dose-dependent increase in PF proliferation and the release of IL-1 and IFN-gamma from PM phi and PLy. Meanwhile, the cytoplasmic parameters PF, PM phi, and PLy Ca2+ in the uremic patients were below normal; they exceeded the norm with a Ca2+ concentration of 1.75 and 2 mmol/L and were normal with a Ca2+ concentration of 1.25 mmol/L. These data suggest that in CAPD patients the use of a physiological Ca peritoneal dialysis solution (1 and 1.25 mmol/L) may be useful in reducing the proliferation of PF and the production of IL-1 and IFN-gamma thus preventing peritoneal sclerosis.

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