p. 219 - 226 TRANSPORT ACTIF DE Na+ A TRAVERS LES EPITHELIUS CHEZ LA TRUITE ARC-EN-CIEL (Salmo gairdneri irideus GIBBONS) ACCLIMATEE EN EAU MARINE V. Craciun 1), Margareta Craciun 1), I. Neacsu 1) ET Ionita Reveica 2) 1) Centre de Recherches Biologiques Iasi 2) Institut Roumain de Recherches Marines Constanta Abstract The results on the activity of Na+ and K+ dependent ATP-ase of the epithelia of the Black Sea adapted rainbow trout (Salmo gairdneri irideus) in comparison with the fresh water maitained rainbow trout are presented. In these conditions the active transport of Na+ and K+ through gills, intestine and kidney is reduced at the marine adapted one.