Effect of extracellular nucleotide hydrolysis on RVD of trout hepatocytes

PAFUNDO, D., MUT, P., PEREZ-RECALDE, M., FACHINO, V., KRUMSCHNABEL, G., SCHWARZBAUM, P.J.

Edinburgo

Congreso; Annual Meeting of the Society of Experimental Biology; 2004

In trout hepatocytes, hypotonic swelling is followed by a compensatory shrinkage called regulatory volume decrease (RVD). It has been postulated that extracellular ATP and other nucleotides may interact with type 2 purinic receptors (P2) to modulate this response. In addition, specific ectoenzymes sequentially dephosphorylate extracellular ATP to adenosine. This can bind to type 1 purinic receptors (P1) and also influence RVD. Accordingly, in this study we assessed the role of extracellular nucleoside 5’-tri- and diphosphates and of adenosine on RVD of trout hepatocytes. The extent of RVD after 40 min of maximum swelling was denoted as RVD40, whereas the initial rate of RVD was called vRVD. In the presence of hypotonic medium (60% of isotonic), hepatocytes swelled 1.6 times followed by vRVD of 1.7 and RVD40 of 60%. Five µM of either ATP, UTP, UDP or ATPgS (P2 agonists) increased vRVD 1.5-2 times, whereas no changes were observed in the values of RVD40. Addition of 100 µM of suramin or cibacron blue (P2 antagonists) to the hypotonic medium produced no effect on vRVD but a 47% inhibition of RVD40. Concerning the effect of P1 activation on RVD, 5 µM adenosine decreased RVD40 to 60% of control values whereas 8-phenil theophyline, a P1 antagonist, increased RVD40 15%. Results indicate that ATP, UTP and UDP are important factors enabling RVD of trout hepatocytes, whereas adenosine inhibits this process.