This work was oriented to studies of sodium and potassium dependent adenosinetriphosphatase, Na+ /K+ ATPase, which is selectively inhibited by cardioactive glycoside, ouabain. The alterations in level of this enzyme were followed in spleen lymphocytes and hippocampus prepared from rats. Detection of Na+ /K+ ATPase has been made by western blot analysis using primary antibodies oriented against α subunit of Na+ /K+ ATPase. Studies of lymphocytes were based on usage of both monoclonal and polyclonal antibodies. In studies of hippocampus monoclonal antibodies were used. The first aim of my work was to determine the alterations in the level of Na+ /K+ ATPase in spleen lymphocytes cultivated in tissue culture (i.e. under in vitro conditions) in the presence of morphine or strong mitogen, concanavalin A (ConA). The second aim of these theses was to determine the changes of Na+ /K+ ATPase α subunit in hippocampus of rats, which were under in vivo conditions exposed to stress lasting 3 days. The stress of experimental animals was induced by deprivation from sleep. The long-term incubation of spleen lymphocytes with 10 μM morphine for 48 hours did not cause a significant change of Na+ /K+ ATPase α subunit level. This result was obtain by analysis of post nuclear fraction (PNS), by use of monoclonal...