Involvement of P2 receptors in regulation of glomerular permeability to albumin by extracellular nucleotides of intra-/extra-glomerular origins.

Plasma filtration through glomerular filtration barrier (GFB) is a key process to maintain fluid and electrolyte homeostasis. GFB consisting of endothelial cells, podocytes and basement membrane restricts passage of albumin but is permeable for smaller plasma molecules. Various biological agents, such as extracellular nucleotides influence activity of cells, which in turn affects permeability of GFB. Nucleotides are released from cells outside and within the glomeruli that activate the purinoceptors - P2Rs classified into ATP-gated non-selective ion channels, P2X receptors (P2XRs), and G-protein-coupled metabotropic P2Y receptors (P2YRs). P2Rs are expressed on cellular components of GFB. P2Rs activation triggers intracellular calcium concentration and calcium-dependent metabolism with subsequent affect on glomerular permeability to albumin. Purinergic-dependent glomerular cell activation also affects the biophysical properties of acelluar glomerular basement membrane (GMB). Finally, P2Rs stimulation may lead to increased proteins excretion in urine. The involvement of P2Rs in increased GFB permeability to albumin may be expected under pathophysiological conditions characterized by increased albumin excretion in urine.