The effect of 4-dimethylamino-3′-methylazobenzene on 14C-labelled amino acid incorporation by rat-liver polysome preparations

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Abstract
The incorporation of C14-labelled amino acids into polysomal protein was studied in a system consisting of polysomes and pH 5 enzyme obtained 4 and 40 hr. after a single intra-peritoneal injection of 4-dimethylamino-3''-methylazobenzene. Labelling of the polysome fraction of preparations of both the 4 hr.-treated and 40 hr.-treated rats was considerably higher than in the normal con-trol. In further experiments on protein synthesis by polysomes from azo-dye-treated rats, the effect of replacing pH 5 enzyme with cell sap was studied. Incorporation of C14-labelled amino acids into polysomal protein was similar to that of the control. Aggregate size of polysomes obtained from rats injected previously with 4-dimethyl-amino-3''-methylazobenaene was studied by sucrose-gradient centrifugation. Polysomes prepared at 4hr. after azo-dye administra-tion contained a considerable amount of large aggregates (approx. 700s), whereas at 40 hr. after administration of the azo-dye the amount of large aggregates was less than in the control. Determination of the ultraviolet spectra of polysome preparations from both normal and azo-dye-treated rats revealed no difference between the preparations. On the other hand, the ultraviolet spectra of cell-sap fractions from the different preparations showed that there is a definite shift in the absorption maximum from 272m[mu] (normal) to 267m[mu], 40hr. after treatment, with an intermediate value of 270m[mu] for the preparation from 4 hr.-treated rats. The absorption minimum changes from 250m (normal) to 245m[mu] for the preparation from 40hr.-treated rats.