Which parameters affect cytosolic free calcium in polymorphonuclear leukocytes of haemodialysis patients?

Background. Cytosolic free calcium ([Ca2+](i)) is an important second messe nger during stimulation in a wide variety of cells, including polymorphonuc lear leukocytes (PMNs). Its mobilization in PMNs is altered in various dise ases such as atherosclerosis and ageing. In chronic haemodialysis (HD) pati ents, both atherosclerosis and accelerated ageing are well know. Therefore [Ca2+](i) in resting PMNs of HD patients was determined along with certain parameters with might affect it, such as recombinant human erythropoietin ( rHuEpo) treatment, calcium-phosphate balance, and biocompatibility of dialy sis membranes. Methods. PMNs were separated by density centrifugation and [Ca2+](i) was de termined by spectrofluorimetry using Quin 2/AM fluorescent dye. Laboratory parameters were determined by standard methods in clinical chemistry. Results. It ws found that [Ca2+](i) in resting PMNs of HD patients not unde rgoing rHuEpo therapy was higher than that of controls. After 12-weeks of r HuEpo therapy, [Ca2+](i) decreased to near normal level. The role of erythr opoiesis in normalization of [Ca2+](i) in resting PMNs was supported by PMN [Ca2+](i) which was elevated in patients who had low haemoglobin (<100 g/l ) or haematocrit (<0.30) values. In some patients, including those receivin g rHuEpo treatment, [Ca2+](i). One possible parameter might be the disturbe d calcium-phosphate metabolism of chronic renal failure, because we found a strong correlation between [Ca2+](i) and plasma iPTH levels in HD patients (r=0.743, P<0.001). [Ca2+](i) was also elevated in PMNs of those patients who had either low plasma calcium or high plasma phosphate levels. PMN [Ca2 +](i) of HD patients correlated positively with the duration of HD (r=0.671 , P<0.001). However, there are no correlation between [Ca2+](i) and patient age. The dialysis procedure itself also transiently increased PMN [Ca2+](i ) HD patients, independently of the type of dialysis membrane. Conclusion. PMN [Ca2+](i) is modulated by various parameters in HD patients , including the degree of anaemia, disturbances of calcium metabolism, and duration of dialysis treatment. The elevated [Ca2+](i) of resting PMNs migh t contribute to altered functions in these cells.