Comparative analysis of P receptor-mediated induction of regulatory volume decrease in cells from teleosts and mammals

ALVAREZ CL, ESPELT MV, PAFUNDO DE, KRUMSCHNABEL G Y SCHWARZBAUM PJ

Innsbruck

Congreso; 26th ESCPB conference; 2009

ESCPB

In most cells hypotonic exposure causes cell swelling followed by ATP release. The accumulated extracellularATP (ATPe)may act on P2 receptors to activate a recovery of cell volume known as volume regulatory decrease (RVD).We have studied the RVD of goldfish hepatocytes, as compared to trout hepatocytes and a human hepatoma cell line (HEPG2). In hypotonic medium the three cell types undergo swelling followed by a non-linear accumulation of ATPe. Cells increased their volume about 1.6 times, with subsequent 60% RVD after 40 min (trout and HEPG2 cells) or no RVD (goldfish). Addition of apyrase (a nucleotide remover) or P2 blockers led to a significant inhibition ofRVD in trout cells, but had no effect in HEPG2. In goldfish hepatocytes extracellular ATPγS (a non-hydrolyzable ATP analogue) induced RVD in a concentration-dependent manner (1–50 μM, K0.5=570 nM), a response which was abolished by antagonists of P2 receptors. Since goldfish hepatocytes do release ATP, we decreased the assay medium several fold to verify if endogenous extracellular ATP could accumulate in sufficient concentrations to trigger RVD. Accordingly, with a 1:40 v/v dilution of cells (height of the medium108μm), goldfish cells had a 56% RVD that could be abolished 73% by P2 antagonists. Thus, as a preliminary conclusion, although an RVD could be observed in goldfish, trout and HEPG2 cells, the activation patterns are different. RVD can be triggered under standard hypotonic conditions (trout and HEPG2), or when the extracellular medium is sufficiently low to accumulate ATPe (goldfish). Up to now, the RVD of HEPG2 cells does not seem to require activation by ATPe.