Evaluation of liver weight changes following a single oral administration of carbon tetrachloride in rats

To evaluate liver weight changes resulting from the primary toxic effect of carbon tetrachloride (CCl4), male and female rats were assigned to a control group, CCl4-treated groups administered a single po dose of 100 microliters (males only) or 200 microliters CCl4/100 g body wt, or a "hold" group in which the body weight change of the CCl4-treated group was duplicated by imposing restrictions of movement and feeding. Five rats from each group were killed at 1, 2, 3, 4, and 6 days after treatment, and body weight, food intake, and liver weight were tabulated. It was found that presentation of liver weight data in absolute terms may lead to erroneous conclusions, since the absolute liver weights of the CCl4-treated males showed changes similar to those of the control group, as if there had been no effect of CCl4 on liver weight. Furthermore, the results for the hold group (males and females) showed that there was not a linear relationship between liver weight and body weight during the period of rapid decrease in body weight, suggesting that comparisons made in terms of relative organ weights do not necessarily take proper account of differences in body weight. From the profile of the percentage absolute liver weight increases (delta W) of the CCl4-treated group from the levels in the hold group, it was concluded that CCl4 does induce an increase in liver weight following a single dose, and the effect on liver weight reached a maximum at 24 to 48 hr. These results demonstrate the need for great care in evaluating the direct effect of chemicals on organ weight when rapid changes in body weight are also occurring.