The effects of carbon tetrachloride on rat liver microsomes during the first hour of poisoning in vivo, and the modifying actions of promethazine

The effects of an oral administration of carbon tetrachloride on various liver microsomal and supernatant components were studied 1hr. and 2hr. after dosing. The modifications of such early changes resulting from a concomitant administration of promethazine together with the carbon tetrachloride were also investigated. The microsomal components studied were: cytochromes P-450 and b5; inorganic pyrophosphatase; NADH– and NADPH–cytochrome c reductases; NADH– and NADPH–neotetrazolium reductases; a lipid-peroxidation system associated with the oxidation of NADPH and stimulated by ADP and Fe2+. NAD– and NADP– DT-diaphorases were measured in the supernatant solution remaining after isolation of liver microsomes, and the distribution of RNA phosphorus between the microsomes and supernatant solution was also determined. Carbon tetrachloride produced a rapid fall in inorganic pyrophosphatase activity, a rather slower decrease in cytochrome P-450 content of the microsomes and small increases in the activities of NADH–cytochrome c reductase and neotetrazolium reductases. The activities of NADPH–cytochrome c reductase, the NADPH–ADP/Fe2+-linked lipid-peroxidation system, DT-diaphorases and the content of cytochrome b5 in the microsomes were unchanged. There was also a loss of RNA phosphorus from the microsomes into the supernatant solution. The RNA phosphorus redistribution, the decrease in inorganic pyrophosphatase and the increases in neotetrazolium reductase activities were at least partially prevented by a concomitant dosing with promethazine. However, the decrease in cytochrome P-450 was not affected by promethazine treatment. These early changes are discussed in terms of the liver necrosis produced by carbon tetrachloride and which is greatly retarded in its onset by the administration of promethazine.