title: Zidovudine [AZT] myotoxicity: quantitative separation of AZT effects on proliferation and differentiation of muscle cells in vitro. Lack of myotoxicity potentiation by retrovirus.
abstract: We compared quantitatively the myotoxicity of 3'-azido-2',3'-dideoxythymidine (AZT) against uninfected and ts1 retrovirus infected mouse skeletal muscle (ATCC CRL 1772) cells at different stages of maturation in vitro. The AZT half inhibitory concentration (IC50) for myoblast proliferation was determined for uninfected myoblasts and parallel cultures infected with ts1 virus. The AZT IC50 for muscle cell differentiation was determined in cultures where myoblasts were grown to confluence and then changed to the fusion medium to which AZT was added at increasing concentrations. Creatine kinase activity was used as a marker of muscle cell differentiation and was determined in homogenates after 7 days. Total cellular mitochondrial DNA was analyzed by Southern blotting. The estimated AZT IC50 for muscle cell proliferation (2-5 microM) was significantly less than the AZT IC50 for muscle cell differentiation (100 microM). Infection with ts1 retrovirus did not significantly shift the IC50 for either proliferation or differentiation of muscle cells. Toxic concentrations of AZT did not cause selective depletion of mitochondrial DNA. The myotoxic effects of AZT on myoblast proliferation and muscle cell differentiation in vitro were quantitatively different and were not changed by productive ts1 retrovirus infection of muscle cells. These results suggest that AZT may impair muscle fiber regeneration in the course of retrovirus associated myopathy. The mechanism of AZT myotoxicity was not explained by alterations in total mitochondrial DNA content.
authors: Neurology Department, University of Wisconsin Medical School, William S. Middleton Memorial Veterans Affairs Hospital, Madison 53792, USA. waclawik@neurology.wisc.edu
authors: A J
authors: AJ
authors: Waclawik
authors: J
authors: J
authors: Vann
authors: G
authors: G
authors: Schmelz
authors: P
authors: P
authors: Szurek
authors: P
authors: P
authors: Lewandoski
authors: B R
authors: BR
authors: Brooks
mesh_terms: D000818:Animals; D019380:Anti-HIV Agents / Q000633:toxicity*; D015139:Blotting, Southern; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003402:Creatine Kinase / Q000378:metabolism; D015342:DNA Probes; D004261:DNA Replication / Q000187:drug effects; D004272:DNA, Mitochondrial / Q000096:biosynthesis; D051379:Mice; D008809:Mice, Inbred C3H; D008854:Microscopy, Electron; D018482:Muscle, Skeletal / Q000473:pathology*; D009135:Muscular Diseases / Q000139:chemically induced* / Q000473:pathology / Q000821:virology; D012192:Retroviridae Infections / Q000473:pathology* / Q000821:virology; D015215:Zidovudine / Q000633:toxicity*
chemical_list: D019380:Anti-HIV Agents; D015342:DNA Probes; D004272:DNA, Mitochondrial; D015215:Zidovudine; D003402:Creatine Kinase