Studies in Protein Metabolism: The Inter-Relationships of Energy Metabolism and Protein Metabolism

Wikramanayake, Thomas Walter (1952) Studies in Protein Metabolism: The Inter-Relationships of Energy Metabolism and Protein Metabolism. PhD thesis, University of Glasgow.

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Abstract

Part I: The relationship between energy intake and nitrogen balance. 1. Experiments are described in which additional carbohydrate (glucose) and additional fat (olive oil) were given to adult rats already receiving an adequate diet. This caused a reduction in urinary N output whether the surfeit was given with dietary protein or 5 to 12 hours apart from the protein. N retentions of similar magnitude were obtained whether the surfeit was given in the form of carbohydrate or an isodynamic amount of fat. 2. Similar experiments were carried out on adult dogs, the additional carbohydrate (sucrose) being given with the protein on one single occasion, and 7 and 12 hours apart from the protein on other single occasions. Nitrogen retention was obtained when sucrose was given within 7 hours of the protein meal. Repeated daily doses of sucrose 12 hours after the protein meal eventually produced a retention of N of equal magnitude to the amount stored when sucrose was given with the protein. 3. Experiments were also carried out on 4 human subjects receiving adequate diets. Additional carbohydrate (sucrose) reduced the urinary N output whether it was taken with the diet or 5 1/2 hours after the last meal of the day. When the sucrose was taken apart from the meals, a lag period of 24 to 48 hours was observed before the urinary N output was reduced. 4. It has been concluded that carbohydrate and fat act interchangeably as energy sources in sparing protein; they do not need to be taken along with dietary protein to exert this sparing action. This N sparing effect is probably produced by increasing the tissue concentration of some energy-yielding metabolite which is necessary for the synthesis of protein. Part II: The effect of energy intake on the metabolism of adenosine triphosphate in the liver. 1. Experiments are described in which energy in the form of olive oil was given to rats receiving a fixed basal diet. This caused a significant change in the ATP/ADP ratio, which increased linearly with the amount of energy added. 2. The significance of the ATP/ADP ratio is discussed, and it has been concluded that energy intake influences protein synthesis by affecting the "phosphate potential". Part III: The influence of energy intake on the metabolism of ribonucleoproteins. 1. A study has been made of the effect of variations in energy intake on the amount of ribonucleic acid (RNA) in the rat liver, and on the uptake of labelled phosphorus by RNA. 2. When the diet contained protein, addition of energy in the form of carbohydrate or fat resulted in a considerable increase In the amount of RNA per liver: when the diet lacked protein, an increase in energy intake caused only a slight change in the amount of RNA. 3. The uptake of by RNA, as measured by relative specific activity, behaved in the opposite way. Uptake was not affected by variations In energy intake when the diet contained protein, but it was considerably stimulated by addition of energy to the protein-free diet. 4. These results indicate that the absolute rate of incorporation of phosphorus into RNA is dependent on energy intake. At each level of protein intake, addition of energy increases the total number of P atoms incorporated into RNA, in one case by an increase in the amount of RNA per liver without a change in the percentage of P atoms Incorporated in a given time, in the other case by an increase in the incorporation rate to compensate for the much smaller change in the amount of RNA per liver. Part IV: The effect of energy intake on the metabolism of liver phospholipid. 1. Experiments similar to those described in Part III were carried out on rats, to study the effect of variations in energy intake on the amount of phospholipid per liver, and on the uptake of labelled phosphorus by the liver phospholipid. 2. On a protein-containing diet, addition of energy (carbohydrate) produced a marked increase in the amount of phospholipid per liver; when the diet was protein-free, the phospholipid per liver decreased slightly with the addition of energy. 3. The uptake of 32P, as measured by the relative specific activity, was increased by addition of energy, whether the diet contained protein or not, the change being greater in the latter case. 4. The absolute rate of Incorporation of phosphorus was greater on a protein-containing diet, the increase in the relative specific activity on a protein-free diet being balanced by a drop in the total quantity of phospholipid per liver. It has been concluded that the liver phospholipid differs from RNA in that the absolute rate of incorporation of phosphorus is affected by the level of protein intake as well as by the intake of energy. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Physiology, Nutrition
Date of Award: 1952
Depositing User: Enlighten Team
Unique ID: glathesis:1952-78908
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 14:43
Last Modified: 30 Jan 2020 14:43
URI: http://theses.gla.ac.uk/id/eprint/78908

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