Kinetics of ATP release and cell volume regulation of hyposmotically challenged goldfish hepatocytes

PAFUNDO DIEGO; CHARA OSVALDO; FAILLACE M. PAULA; KRUMSCHNABEL G.; SCHWARZBAUM PABLO JULIO

AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY, INTEGRATIVE AND COMPARATIVE PHYSIOLOGY

The American Physiological Society (APS)

Lugar: Bethesda, Maryland; Año: 2008 vol. 294 p. 220 - 233

0363-6119

In most animal cells,hypotonic swelling is followed by a regulatory volume decrease(RVD) thought to prevent cell death. In contrast, goldfish hepatocyteschallenged with hypotonic medium (180 mosM, HYPO) increase theirvolume 1.7 times but remain swollen and viable for at least 5 h.Incubation with ATP
S (an ATP analog) in HYPO triggers a 42%volume decrease. This effect is concentration dependent (K1/2  760nM) and partially abolished by P2 receptor antagonists (64% inhibition).A similar induction of RVD is observed with ATP, UTP, andUDP, whereas adenosine inhibits RVD. Goldfish hepatocytes releasemore than 500 nM ATP during the first minutes of HYPO with noinduction of RVD. The fact that similar concentrations of ATP
S didtrigger RVD could be explained by showing that ATP
S induced ATPrelease. Finally, we observed that in a very small extracellular volume,hepatocytes do show a 56% RVD. This response was diminished byP2 receptor antagonists (73%) and increased (73%) when the extracellularATP hydrolysis was inhibited 72%. Using a mathematicalmodel, we predict that during the first 2 min of HYPO exposure theextracellular [ATP] is mainly governed by ATP diffusion and by bothnonlytic and lytic ATP release, with almost no contribution fromecto-ATPase activity. We show that goldfish hepatocytes under standardHYPO (large volume) do not display RVD unless this istriggered by the addition of micromolar concentrations of nucleotides.However, under very low assay volumes, sufficient endogenous extracellular[ATP] can build up to induce RVD.