Expression of the mitochondrial genome in HeLa cells. IX. Effect of inhibition of mitochondrial protein synthesis on mitochondrial formation.

The effect of selective inhibition of mitochondrial protein synthesis by chloramphenicol at 40 or 200 microg/ml on the formation of mitochondria in HeLa cells was investigated. HeLa cells, under the conditions used in the present work, grow at a decreasing rate for at least four cell generations in the presence of 40 microg/ml chloramphenicol, and for two generations in the presence of 200 microg/ml chloramphenicol. The progressive cell growth inhibition which begins after 2 days of exposure of the cells to 40 microg/ml chloramphenicol is immediately or gradually reversible, upon removal of the drug, for periods up to at least 8 days of treatment, though there is a progressive loss of cloning efficiency. In cells which have been treated for 6-7 days with 40 or 200 microg/ml of chloramphenicol, mitochondrial protein synthesis occurs at a normal or near-normal rate 1 h after removal of the drug. Mitochondria increase normally in number and show a normal size and amount of cristae in the presence of either concentration of drug. However, in 4-5% of the mitochondrial profiles the cristae appear to be arranged in unusual, circular, looped or whorled configuration.