The activity of alkaline and acid DNase after in vitro treatment of isolated hepatocytes with NO donor (SNP) or peroxynitrite. The isolation of hepatocytes was done according to the method already published , by using a 1% collagenase dissolved in RPMI 1640 medium. Hepatocytes, isolated from 8 Male Sprague-Dawley rats, were dissolved in a physiological saline solution in a concentration of approximately 108cells/ml. They were divided into seven groups (each comprising 8 samples), exposed to either SNP (0.1, 1 and 10 mmol) or peroxynitrite (0.03, 0.3 and 3 mmol) for a period of 1 hour at 37°C. Given in vitro concentrations were calculated according to the literature data . The activity of alkaline and acid-DNase was measured by the methods of Bartholeyns et al.  and acid soluble nucleotides were determined spectrophotometrically at 260 nm. The enzyme activity was expressed as U/g protein. Data (n = 8) in graph is putted as: Mean + SD.