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Purinergic receptors and regulatory volume decrease in seabream (Sparus aurata) hepatocytes: a videometric study

Torre, Agata, Trischitta, Francesca, Faggio, Caterina
Fish physiology and biochemistry 2012 v.38 no.6 pp. 1593-1600
Sparus aurata, adenosine, adenosine triphosphate, agonists, antagonists, apyrase, hepatocytes, metabolites, receptors, suramin, verapamil
The response of isolated hepatocytes of Sparus aurata to hypotonic stress was studied by the aid of videometric methods with the aim to investigate the possible involvement of ATP in the regulatory volume decrease (RVD). This study confirms our previous observations showing the ability of these cells to undergo RVD. In addition, it shows that the homeostatic response was inhibited by apyrase, an ATP scavenger, thus suggesting the involvement of extracellular ATP in the RVD response. Experiments performed in the presence of ATPγS or adenosine, agonists of P₂ and P₁ receptors respectively, and in the presence of suramin or 8-PT, antagonists of P₂ and P₁ receptors respectively, suggest that ATP exerts its stimulatory effect on the homeostatic response by interacting with P₂ receptors. On the other hand, the activation of P₁ receptors by ATP metabolites produces opposite effects. In an attempt to clarify the mechanisms involved in ATP release from the cell, we performed some experiments with known inhibitors of the possible mechanisms of regulated ATP release. The results we obtained let us to suppose that the mechanism allowing the exit of ATP from the cell is verapamil sensitive suggesting the involvement of the P-glycoprotein.