Hormonal influences on the incorporation of injected precursors into the protein and ribonucleic acid of liver cytoplasm

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Abstract
Untreated hypophysectomized rats, hypophysectomized rats treated with growth hormone and adrenalectomized rats were compared with intact rats kept on the same food intake, with respect to the incorporation of PL-(1-C14) leucine into liver protein and of (6-C14) orotic acid into liver ribonucleic acid (RNA). The liver from each animal was separated by differential centrifuging into a nuclear fraction and a cytoplasmic fraction. The latter was centrifuged to give a mitochondrial fraction, a fluffy layer, a microsomal fraction, and a supernatant fraction which was, in some experiments, further centrifuged to sediment an ultracentrifugal fraction. Hypophysectomized rats showed a decreased recovery of labeled leucine in cytoplasmic protein, each of the fractions sharing in this decrease. The recovery tended to be even lower after growth-hormone treatment in the case of the cytoplasm as a whole and of the microsomal fraction. Adrenalectomized rats showed a decreased recovery of leucine in the protein of the cytoplasm as a whole and of the microsomal fraction, but the decrease was smaller than that observed after hypophysectomy. Hypophysectomized rats showed a decreased recovery of labeled orotic acid in the RNA of the mitochondrial fraction, the fluffy layer, and the microsomal fraction. These effects of hypophysectomy were not significantly influenced by growth hormone. Adrenalectomized rats showed a decreased recovery of orotic acid in the RNA of the microsomal fraction, but an increased recovery in that of the cytoplasm as a whole, of the supernatant fraction, and of the ultracentrifugal fraction.