Protection by propylthiouracil against carbon tetrachloride-induced liver damage

Rats given a single intragastric dose of carbon tetrachloride (CCl4), 0.25, 0.50, or 1.0 ml per kg) showed a dose-dependent increase in SGOT, serum ornithine carbamyltransferase, and liver necrosis (graded histologically as 0 to 4+) 24 hr after the treatment. Daily intubation with propylthiouracil (PTU) for 10 days in doses of 5 to 50 mg per kg significantly reduced the elevation of SGOT activity, completely suppressed the serum ornithine carbamyltransferase changes, and reduced the degree of necrosis found 24 hr after the intragastric administration of CCl4. Similar protection was found when CCl4 was given intraperitoneally. When PTU was given in liguid diets for 6 days, protection against CCl4 was increased. PTU did not affect the absorption or covalent binding of 14CCl4 to lipids or proteins. Also, control and PTU-treated rats did not differ with respect to glucose-6-phosphatase activity and conjugated diene production after CCl4. Thus, it has been observed that PTU affords partial protection against some end-stage consequences of CCl4 liver injury such as cell necrosis and release of intracellular enzymes. However, PTU afforded no protection against early chemical effects such as covalent binding of CCl4 carbon, lipid peroxidation, or loss of glucose-6-phosphatase. Therefore, it is concluded that the mechanism of the PTU effect comes into play after the initial effects of CCl4 are exerted and in some unknown manner modulates the expression of these early effects.