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Incorporation of Valine-1-C¹⁴ into Serum and Tissue Proteins of Rats Fed Torula Yeast Diets

Section on Experimental Liver Diseases, LEP, National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland

The incorporation of intraperitoneally injected valine-1-C¹⁴ into proteins of serum and various tissues was measured in rats fed vitamin E-deficient Torula yeast diets during the latent, prenecrotic phase of dietary necrotic liver degeneration. As compared with controls fed on McCollum's wheat-casein diet or on a 20% casein regimen, incorporation of valine into liver and serum protein was found considerably enhanced.

The accelerated valine incorporation was not directly related to the prenecrotic condition of the animal: The necrosis-preventing supplements, vitamin E or selenite, with or without addition of DL-methionine, were without effect; L-cystine also had no influence. However, a combination of both vitamin E and selenite with methionine significantly reduced the incorporation of valine into liver protein. The observed changes are independent of the growth rate of the animals.

When a mixture of essential amino acids, with methionine, was fed at a 10% level, normal rates of valine incorporation were established in liver and serum protein. The same normalization was obtained by a combination of 5% essential amino acids, with methionine, and 5% nonessential amino acids. In the absence of methionine, the mixture of the essential amino acids did not reverse the enhanced rate of incorporation. Supplementation of 10% of a mixture of nonessential amino acids, with or without methionine, did not reverse the condition, but caused a further increase of the rate of valine incorporation. Thus, the enhancement of valine incorporation appears to be a sign of an insufficient or imbalanced supply of essential amino acids.

In subcellular fractions of liver, the maximal increase of the rate of incorporation was noted in mitochondria, followed by that in the supernatant, microsomes and nuclear fraction.

The increase in valine incorporation was observed in all organs except muscle and spleen. Maximal enhancement occurred in the liver (+80%), heart (+55%) and kidney (+49%).

A characteristic difference occurred in the rates at which the radioactivity disappeared from serum and especially liver protein. During the first two days following the injection, the disappearance of valine was delayed in animals fed the basal Torula yeast diet.

Manuscript received 23 August 1962.

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				H. Sidransky, T. Staehelin, and E. Verney Protein Synthesis Enhanced in the Liver of Rats Force-Fed a Threonine-Devoid Diet Science, November 6, 1964; 146(3645): 766 - 768. [Abstract] [PDF]