Effects of type 2 purinic receptor activation on RVD of trout hepatocytes

PAFUNDO, DE; FACHINO, V; PEREZ-RECALDE, M; KRUMSCHNABEL, G; SCHWARZBAUM, PJ

San Carlos de Bariloche, Argentina

Congreso; XXXII Reunión anual de la Sociedad Argentina de Biofísica.; 2003

In trout hepatocytes, hyposmotic conditions induce cell swelling and subsequent efflux of ion and water, thereby promoting a down regulation of cell volume called RVD. It has been postulated that RVD is triggered by the interaction of extracellular ATP with P2 purine receptors. We used trout hepatocytes to assess the importance of extracellular ATP in the regulation of cell volume. In hyposmotic medium, the cells swelled up to aprox. 160% of the isosmotic value, followed by 26.6 ± 0.8 % and 53.5 ± 1.7 % RVD after 20 and 40 min. Suramine and cibacron blue, two antagonists of P2 receptors, generated an inhibition of 27-32 % (20 min) and 48-50 % (40 min) of RVD, whereas ATP and ATPgS (P2 agonists) increased RVD by 66-77 % (20min) and 12-17 % (40 min). In separate experiments, we added an excess of apyrase and Na+/K+ATPase to cell suspensions to scavenge any possible ATP present in the extracellular medium. Incubation of cells in hyposmotic medium containing these scavengers decreased RVD by 70-100% with respect to controls. Results indicate that ATP is an important factor enabling RVD of hyposmotically induced trout hepatocytes.