Inhibition of Protein Synthesis in Mammalian Cell-free Systems by Ci-iloramphenicol*, by Austin

Although chloramphenicol is known to inhibit microbial protein synthesis both in intact cells (1-3) and in cell-free systems (4--8), similar inhibition of protein synthesis does not occur in analogous mammalian systems unless large amounts of chloramphenicol are employed (9-12). The difference in sensitivity to chloramphenicol is most striking in cell-free systems, where cellular permeability is not a factor. Thus complete inhibition of protein synthesis in Esckerichia coli cell-free systems can be obtained with 0.15 micromoles of chloramphenicol per ml reaction mixture (7). In contrast, comparatively little inhibition of protein synthesis in mammalian cell-free systems has been obtained with 5 to 10 micromoles of the drug per ml reaction mixture (10, 11). The findings of Djordjevic and Szybalski (13) and of Ambrose and Coons (14) appear to be exceptions to these observations. In these studies inhibition of protein synthesis was obtained in tissue cultures with low levels of chloramphenicol providing the drug was in contact with the cells during periods of active protein synthesis.