Protein reserves and muscle constituents of protein-depleted and repleted cocks

Abstract

I . Body-weight changes and nitrogen balance were studied, together with the concentration of various nitrogenous muscle components, in adult cocks before and after a 6-day period on a N-free diet and again after a 16-day repletion period on diets supplying various amounts and types of dietary N. 2.In the first experiment a comparison was made during the repletion period between a fish-protein supplement and a supplement of glycine + glutamic acid added to an essential amino acid mixture.3. During the depletion period the muscle concentration of RNA, DNA and of two transaminase enzymes decreased significantly ; during the repletion period these components increased again significantly, and usually to levels greater than the pre-depletion concentration.There were no differences in these responses obtained during repletion with the two N supplements, although the cocks given the glycine-glutamic acid supplement differed from those receiving fish protein in being in negative N balance and in losing body-weight during the repletion period.4. In the second experiment one group of depleted cocks was given an essential amino acid mixture alone as the dietary N source and a second group this mixture supplemented by aspartic acid. .A decrease in RNA and in the transaminase enzymes during depletion was followed by a significant increase during repletion, but the increase was greater for the group receiving the aspartic acid than for that receiving only the essential amino acid mixture. 6.It was concluded that adding non-essential amino acids to a maintenance mixture of essential amino acids will permit greater repletion in mature cocks.7. The fluctuations in concentration of RNA and of certain enzymes with dietary protein supply may well be a controlling factor in the regulation of N losses and accretions during protein deficiency and sufficiency.8. The relative constancy of muscle DNA in contrast to the fluctuations in other nitrogenous muscle constituents provides additional support for the concept of protein reserves.The amount of body nitrogen loss in adult cocks on a protein-free diet beyond which repletion does not occur with a supplement of non-essential amino acids to a maintenance mixture of essential amino acids has been regarded as a measure of the size of the protein reserve pool (Wessels & Fisher, 1965). This estimate of the magnitude of the body'sprotein reserves was based upon the observations of Shapiro & Fisher (1962) that partial repletion of body N stores could be attained by non-essential amino acid N in adult cocks depleted to the endogenous level of N excretion. Logical support for these experimental findings may be derived from a study by Bas& (1958). Basak showed that the N losses of human subjects kept for a short period on a protein-free diet were primarily non-protein in origin and represented about 6% of the total body N of human adults on a normal diet. This quantity is similar to the estimated magnitude of

RNA Content and Protein Synthesis in Skeletal Muscles of Young Rats: Effects of Protein Deficiency

“…One of the most noteworthy biochemical alterations in muscles of protein-deprived animals is a redueti011 in WNA content. This response has been observed by many investigators (Masters 1963 ;Ashley and Fisher 1967;Young and Alexis 1968;Pond ef al. 1969;Hill et cal.…”

Effect of prior protein nutriture and nitrogen retention on the utilization of nonessential nitrogen in the young adult

“…Although these studies shed little light on the nature of the retained N, they do indicate that nonessential N can and does play an important role in intermediary N metabolism in the body. As a follow-up to the investigation just cited, additional adult cocks were N-depleted on a protein-free diet (Ashley and Fisher, 1967). One group was fed a maintenance mixture of essential amino acids only, which constitutes an inadequate amount of total N; a second group was given the same diet but with additional N in the form of aspartic acid to meet not only the maintenance needs for essential amino acids but also the total N needs to permit repletion.…”

The effects of dietary supplementation with lysine and methionine on body and tissue composition in the pig

“…The higher level of lysine in the liver obtained in the OL group is similar to the results of Dalgliesh and Tabechian (1956) who observed that after a labelled amino acid solution had been administered to rats by stomach tube, the activity of the 'protein-bound' fraction in liver, as well as in muscle, increased. In the past few years many reports have given attention to the controversial concept of labile body protein reserves contributing to the free amino acid pools of the body (Holt, Halac and Kajdi, 1962;Holmes, 1965;Fisher, 1967;Munro, 1964;Yuile, Lucas, Neubecker, Cochrane and Whipple, 1959;Ashley and Fisher, 1967;Allison, Wannemacher, Banks and Wunner, 1964). Results of an investigation on dogs reported by Van Slyke and Meyer (1913a, b) also show that musculature is the major reservoir of amino acids, although the percentage content of amino acids in muscle is less than in liver compared with the normal dogs.…”