RESUMEN
BACKGROUND: P2X(7) receptors intervene with lymphocyte activation and are responsible for multiple processes, including calcium influx. Here, we studied the participation of P2X(7) receptors in disturbed intracellular calcium homeostasis regulation in early-stage chronic kidney disease (CKD). METHODS: The study involved 20 healthy volunteers and 20 CKD stage 2-3 patients. The free cytosolic calcium concentration ([Ca(2+)](i)) was measured using fluorimetry. The P2X(7) pore function was evaluated by the fluorescent dye ethidium bromide. RESULTS: In peripheral blood mononuclear cells (PBMCs) of patients, [Ca(2+)](i), intracellular calcium stores and the capacitative calcium entry were increased when compared with healthy subjects. The agonist of P2X(7) receptor BzATP caused a sustained increase in [Ca(2+)](i) in both groups, but the effect was smaller in patients. The antagonist at the P2X(7) receptor KN-62 reduced [Ca(2+)](i) in patients, but had no effect in healthy subjects. In patients, the permeability of ethidium bromide through P2X(7) pores, as well as through BzATP-activated and KN-62-inhibited pores, was distinct from permeability in healthy volunteers. CONCLUSIONS: These results demonstrate that the calcium signaling pathway in PBMCs of CKD patients is defective already in CKD stage 2-3, and the pore-forming P2X(7) receptors are involved in these pathophysiological processes.