Comparison of isoproterenol-induced changes in lysosomal enzyme activity in vivo and in vitro

Isoproterenol was used as a drug which, when administered in high doses, is able to induce lysosomal enzyme activity changes in in vivo conditions. We correlated lysosomal enzyme activity in the absence and presence of isoproterenol, obtained in whole animals and in HeLa and HepG2 cells in tissue culture. In vivo experiments: male Wistar rats (270-300 g) were treated subcutaneously with isoproterenol in various doses. Effect of isoproterenol on lysosomal enzyme activity was assayed in the heart after differential centrifugation. In vitro experiments: Isoproterenol in concentrations 0.1-100 microg/ml was added to HeLa and HepG2 cells and the activity of lysosomal enzyme was measured in the cell homogenate. In the sedimentable and nonsedimentable fractions of the rat myocardium, the isoproterenol-induced changes in the activity of lysosomal enzyme were time-and dose-dependent. In HeLa cells, isoproterenol administration caused a dose-dependent increase of lysosomal enzyme activity, while in HepG2 cells the activity remained unchanged. Thus the isoproterenol-induced changes in lysosomal enzyme activity in the rat myocardium were comparable with the results found in vitro in HeLa cells.