DNA repair in primary cultures of rat hepatocytes.


culture system has several unique properties that make it attractive for use in short-term studies aimed at exploring biochemical changes caused by carcinogenic agents. One such property is their ability to respond to a variety of hormonal stimuli through induction of various metabolic processes(2, 3, 13, 14, 20, 28, 41) including DNAsynthesis (34) and cell replication (18). A second important property concerns the broad drug-metabolizing capabilities of the liver as manifested by the cultured hepatocytes. Some work with this cell system indicated that the drug-metabolizing capacity of the cultured hepatocytes, as represented prin cipally by cytochrome P450 content, declined quickly (2, 6). However,other recent studies indicate that alteration of culture conditions and/or inclusion of key hormones in the culture medium allow the maintenance and/or the actual induction of cytochrome P-450 (4, 21 , 23, 24). Preliminary reports from this laboratory (46, 47, 49) and studies by Williams (43—45) and Michalopoulos et al. (22) also indicate that, at least during the first day or 2 of culture, rat hepatocytes can convert a number of procarcinogens to forms capable of damaging their DNA. This ability was revealed by measuring DNA repair as unscheduled DNA synthesisfollowing treatment with the compounds with the useof autoradiography (43—45) or analytical (22, 46, 47, 49) techniques and by their use as a drug-metabolizing feeder layer for enhancing mutagenesis in established liver cell lines (35). The ability of hepatocytesto metabolize prohepatocarcin ogens to forms that damage DNA, thus stimulating its repair, can be considered to be a “bioassay― for drug metabolizing capacity. Perhaps it may be more meaningful in terms of cell function than an in vitro enzymatic assay for drug-metabolizing enzymes. Although indirect, the induc tion of DNA repair represents a relatively reliable indicator of the prior occurrence of genetic damage caused by chemical carcinogens (37, 38). The recent report by Wil hams (45) demonstrates that repair is stimulated in the cultured hepatocytes by chemicals known to be carcino genic but not by a weak carcinogen and several noncarcin ogens. However, Williams (45) used autoradiography to detect unscheduled DNA synthesis. While this technique does allow quantitation when grain counting is used, it may not be sensitive enough to facilitate a precise quantitative comparison of the amount of repair stimulated by different chemicals. However, precise quantitative comparisons ob tamed by methods less tedious than grain counting are desirable if the hepatocyte culture system is to be used to screen agents for their potential to inflict genetic damage on mammalian cells. Our laboratory is involved with developing and further characterizing the primary hepatocyte culture system for studies on various aspects of the mechanisms involved in carcinogenesis and for use as a screening system. One of our goals is to investigate the DNA repair capacity of the ABSTRACT

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@article{Yager1978DNARI, title={DNA repair in primary cultures of rat hepatocytes.}, author={James D. Yager and Joyce Agati Miller}, journal={Cancer research}, year={1978}, volume={38 12}, pages={4385-94} }