Toxicity assessment of papaverine hydrochloride and papaverine-derived metabolites in primary cultures of rat hepatocytes.

The present study was undertaken to assess and compare the toxic effects of papaverine hydrochloride and its metabolites. Primary cell cultures of rat hepatocytes were treated with papaverine (papaver), 3'-O-desmethyl (3'-OH), 4'-O-desmethyl (4'-OH), and 6-O-desmethyl (6-OH) papaverine at 1 x 10(-5), 1 x 10(-4), and 1 x 10(-3) M for 4, 8, 12, and 24-h periods. Cell injury was determined by: a) cell viability using the trypan blue exclusion test; b) cytosolic enzyme leakage of lactate dehydrogenase and aspartate aminotransferase; c) morphologic alterations; and d) lactate:pyruvate (L:P) ratios. Cell cultures showed concentration- and time-dependent toxic responses. For example, a decrease in cell viability and an increase in enzyme leakage were observed after cell treatment with 1 x 10(-4) and 1 x 10(-3) M papaver for 8 h; 1 x 10(-3) M 6-OH papaverine for 8 h and 1 x 10(-4) M for 24 h; and 1 x 10(-3) M 4'-OH papaverine for 24 h (P less than 0.05). Furthermore, changes in morphology correlated to cell viability and enzyme release in those cultures treated with papaver, 4'-OH and 6-OH papaverine. Some of these changes included size deformation, cell detachment from the dishes, and cell necrosis. On the other hand, an increase in L:P ratios (P less than 0.05) was detected with papaver as early as 8 h with 1 x 10(-4) and 1 x 10(-3) M and 12 h with 1 x 10(-5) M; 6-OH showed an increase in L:P ratios at 8 h with 1 x 10(-3) M and 12 h with 1 x 10(-4) M; these changes were evident with with 4'-OH at 12 h with 1 x 10(-3) M. In contrast, cells treated with 3'-OH papaverine did not show significant damage with any time period and concentration used in this study. The results of this study indicate that papaverine-derived metabolites are less cytotoxic than its parent compound, papaver. The toxicity was ranked as follows: papaver greater than 6-OH greater than 4'-OH greater than -3'-OH.