The effects of polyuridylic acid on phenylalanine incorporation by subcellular fractions from carbon tetrachloride-poisoned rat liver

Abstract

Ribosomes and microsomes isolated from the livers of rats that had received CCI4 1 hr. previously had decreased endogenous capacity to incorate amino acid. The capacity of the isolated structures to respond to a synthetic messenger, polyuridylic acid, and to incorporate phenylalanine was investigated. It was found that ribosomes from CCl4-treated animals, prepared with detergent and at high ionic strength, could be restored to the same specific activity as control particles with polyuridylic acid but that these particles required more Mg2+ in the incubation mixture. Microsomes could also be stimulated to control activities with polyuridylic acid, but had a narrow optimum range of Mg^+ concentration. Microsomes prepared from poisoned animals could be preprogrammed with polyuridylic acid to a significantly greater degree than could control particles, and this response was greater with increasing Mg^+ concentrations. These data suggested that in CCI4 poisoning the messenger-ribosome interaction was altered. Attempts to deprogramme particles from control and treated animals resulted in decreased endogenous activity of both particles and a decreased capacity for the treated particles to be restored with the synthetic messenger. It is suggested that 2 effects are present in CCI4 poisoning, namely an alteration of the messenger-ribosome interaction and an increased lability of the ribosome, as either separate or related events.