Brambilla G, Martelli A
Institute of Pharmacology, University of Genoa, Italy.
Mutat Res. 1992 Aug;272(1):9-15. doi: 10.1016/0165-1161(92)90004-6.
The in vitro hepatocyte DNA-repair assay is a widely used useful method in assessing the genotoxic activity of both directly and indirectly acting chemical agents. This article discusses the criteria presently employed in the autoradiographic evaluation of unscheduled DNA synthesis, and suggests that the subtraction of either the average or the highest cytoplasmic grain count, usually carried out to obtain the net nuclear grain count, may represent a potential source of errors when the test compound is a weakly genotoxic or a non-genotoxic agent. As a matter of fact, a response can be classified as positive or negative depending on the procedure used to quantitate the cytoplasmic background, and the subtraction of this background from the nuclear count is not founded on a sound theoretical basis because of the following reasons: the different nature of the processes responsible for the generation of nuclear and cytoplasmic grains; and the quantitatively different effect that the test compounds may have on the nuclear and the cytosolic labelling.
体外肝细胞DNA修复试验是评估直接和间接作用化学剂遗传毒性活性的一种广泛应用的有用方法。本文讨论了目前用于非程序性DNA合成放射自显影评估的标准，并指出，当测试化合物是弱遗传毒性或非遗传毒性剂时，通常为获得净核颗粒计数而进行的平均或最高细胞质颗粒计数的减法可能是误差的潜在来源。事实上，根据用于定量细胞质背景的程序，反应可分为阳性或阴性，并且从核计数中减去该背景并非基于可靠的理论基础，原因如下：负责产生核颗粒和细胞质颗粒的过程性质不同；以及测试化合物可能对核标记和胞质标记产生的定量不同的影响。
