Positive and negative control observations for the in vivo/in vitro rat liver assay for unscheduled DNA synthesis (UDS).

Positive and negative control data are shown for greater than 50 experiments conducted using the in vivo/in vitro rat liver unscheduled DNA synthesis (UDS) assay. In this assay, animals are dosed with the test agent and the liver is subsequently assessed for UDS by autoradiography and grain counting. The combined corn-oil negative control gave a value of -2.54 +/- 1.4 net gains (NG +/- SD; n = 77) and the positive control agent 6-p-dimethylaminophenylazobenzothiazole (6BT, dosed in vivo, animals sampled at 12 h) gave a value of +28.3 +/- 16.0 NG (+/- SD; n = 51). These data are briefly discussed, as are the reasons why this laboratory employs an in vivo (as opposed to an in vitro) positive control in each experiment.