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This Article Full Text Full Text (PDF) All Versions of this Article: 294/1/R220    most recent 00522.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Pafundo, D. E. Articles by Schwarzbaum, P. J. Search for Related Content PubMed PubMed Citation Articles by Pafundo, D. E. Articles by Schwarzbaum, P. J.

COMPARATIVE AND EVOLUTIONARY PHYSIOLOGY

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

¹Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina; ²Instituto de Física de Liquídos y Sistemas Biológicos, La Plata, Provincia de Buenos Aires, Argentina; ³Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina; and ⁴Division of Developmental Immunology, Innsbruck Medical University, Innsbruck, Austria

Submitted 19 July 2007 ; accepted in final form 8 October 2007

In most animal cells, hypotonic swelling is followed by a regulatory volume decrease (RVD) thought to prevent cell death. In contrast, goldfish hepatocytes challenged with hypotonic medium (180 mosM, HYPO) increase their volume 1.7 times but remain swollen and viable for at least 5 h. Incubation with ATPS (an ATP analog) in HYPO triggers a 42% volume decrease. This effect is concentration dependent (K_1/2 = 760 nM) and partially abolished by P2 receptor antagonists (64% inhibition). A similar induction of RVD is observed with ATP, UTP, and UDP, whereas adenosine inhibits RVD. Goldfish hepatocytes release more than 500 nM ATP during the first minutes of HYPO with no induction of RVD. The fact that similar concentrations of ATPS did trigger RVD could be explained by showing that ATPS induced ATP release. Finally, we observed that in a very small extracellular volume, hepatocytes do show a 56% RVD. This response was diminished by P2 receptor antagonists (73%) and increased (73%) when the extracellular ATP hydrolysis was inhibited 72%. Using a mathematical model, we predict that during the first 2 min of HYPO exposure the extracellular [ATP] is mainly governed by ATP diffusion and by both nonlytic and lytic ATP release, with almost no contribution from ecto-ATPase activity. We show that goldfish hepatocytes under standard HYPO (large volume) do not display RVD unless this is triggered by the addition of micromolar concentrations of nucleotides. However, under very low assay volumes, sufficient endogenous extracellular [ATP] can build up to induce RVD.

extracellular ATP; water transport; ectonucleotidases