RESPIRATORY ENZYMES AND MITOCHONDRIAL MORPHOLOGY OF HELA AND L CELLS TREATED WITH CHLORAMPHENICOL AND ETHIDIUM BROMIDE

Abstract

Exposure of HeLa and L cells to chloramphenicol causes a progressive dose-dependent decrease in cytochrome oxidase and succinate-cytochrome c reductase activities, concomitant with an increase in the amount of cytochrome c . At 2-3 days, the specific activities of the enzymes have fallen to about one-half of control values ; the mitochondria appear swollen . By day 5, enzyme activities are about one-quarter of control values ; the mitochondria are more swollen, with disorientation and disintegration of cristae . By day 6-8, after three generations, growth has stopped, enzyme activities are approximately the same as on day 5, and cytochrome c content has reached 170% of control value. Mitochondria show severe changes, cristae being affected more than peripheral inner membrane . The number of profiles continues to be nearly normal . After 30 days, cytochrome oxidase activity remains low but now there are mitochondria in intermediate and condensed configuration . There is a gradual accumulation in the cytoplasm of smooth membrane elements . If chloramphenicol is removed, cells recover . Ethidium bromide treatment for up to 8 days yields results virtually identical to those obtained with chloramphenicol . Cells treated with 10-' M KCN show a decrease in cytochrome oxidase activity to about one-third of control value and an elevated amount of cytochrome c . Only a small number of mitochondria appear damaged . Autochthonous mitochondrial syntheses appear to be essential for the organization of the cristae . When cytochrome oxidase activity is impaired, a regulatory mechanism for cytochrome biosynthesis geared to mitochondrial function may be lacking, resulting in an increase in cytochrome c content .imbalance of cytochrome syntheses (7, 8) accompanied by defects in mitochondrial ultrastructure

Comparison of mitochondrial morphology, mitochondrial DNA content, and cell viability in cultured cells treated with three anti-human immunodeficiency virus dideoxynucleosides

“…The ultrastructural changes associated with these dideoxynucleosides included swollen or enlarged mitochondria and the loss and distortion of cristae, which sometimes formed concentrically arranged rings. These mitochondrial ultrastructural changes are similar to those described for HeLa and L cells cultured in the presence of either ethidium bromide or chloramphenicol, which are known to be inhibitors of mtDNA synthesis and protein synthesis, respectively (12,18). Our observations are consistent and extend the observations reported previously (13) that cells cultured in the presence of ddC have reduced mtDNA contents, resulting in significant mitochondrial changes.…”

Mitochondrial DNA Depletion and Respiratory Chain Activity in Primary Human Subcutaneous Adipocytes Treated with Nucleoside Analogue Reverse Transcriptase Inhibitors

“…Various nonadipocyte studies suggested mitochondrial threshold effects (24); however, there is limited information regarding the relevance of such thresholds for adipocytes. Other nonadipocyte studies demonstrated that when mitochondrial replication and protein synthesis are severely inhibited by ethidium bromide and chloramphenicol, there is progressive dose-dependent decrease in cytochrome oxidase and succinate-cytochrome c reductase activities (16). Given that such relationships are difficult to extrapolate, as they seem to be agent and cell type specific, our aim was to investigate the relationship between NRTI-mediated mtDNA depletion and mitochondrial function in primary human subcutaneous adipocytes.…”

Ethidium bromide-induced loss of mitochondrial DNA from primary chicken embryo fibroblasts.

“…three cell doublings reduced the mtDNA content 10-fold, suggesting an arrest of synthesis and progressive dilution of the number of mtDNA copies per cell. On the other hand, it is well documented in cultured vertebrate cell studies that the drug induces, with continuing cell proliferation, the formation of mitochondria with bizarre shapes and reduces substantially their cytochrome b and aa3 content (15,32). Upon the removal of EtdBr from the culture medium, however, mtDNA synthesis resumes (36), and apparently normal, respiration-competent mitochondria are found in succeeding cell generations (24,32).…”