Mechanism of action of carbon tetrachloride on liver cells

Abstract

Carbon tetrachloride has long been used to produce experimental liver necrosis, but its mode of action is obscure. In the present work we have investigated the behaviour of the respiratory enzymes in carbon tetrachloride poisoning, using whole cells and cell-free systems obtained by the method of differential centrifugation. Of the cell fractions, the mitochondria were found to be the component attacked by the poison. We have been able to show that the tricarboxylic acid cycle is disorganized. The earliest changes occur between 10 and 15 h after the poison is administered, and consists of inhibition of the oxidation of citrate, malate, octanoate, pyruvate and glutamate, but at this time the oxidation of succinate is unimpaired. The inhibition of malate, glutamate and citrate oxidation can be reversed by the addition of pyridine nucleotide. In the case of pyruvate the inhibition may be partially reversed by the addition of Co I and ATP. The poisoned mitochondria lose pyridine nucleotide at an abnormally fast rate, and at differing times for the different enzymes. Conversely, we have shown that Co I penetrates poisoned mitochondria at a faster rate than normal mitochondria. Administration of choline to poisoned animals delays both the microscopic appearances of injury and the biochemical changes. We have reproduced the biochemical effects of carbon tetrachloride by in vitro treatment of liver homogenates, and we suggest that the mode of action of the agent is a direct attack on the mitochondria. This attack results in a disorganization of the enzyme systems, and is not a specific inhibition of any one of them. The rate of incorporation of 32 P into mitochondrial phospholipid has also been studied, and found to be somewhat increased in carbon tetrachloride poisoning.