Studies in plasma protein metabolism

Fleck, Adam (1964) Studies in plasma protein metabolism. PhD thesis, University of Glasgow.

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In previous studies of plasma protein metabolism it had been demonstrated that catabolism is altered by diet and by the administration of hormones. The aim in this thesis was to decide whether the plasma proteins behaved in the same way as the proteins of the liver in response to the stimuli of injury and changes in the protein content of the diet, and also to elucidate the intermediate steps by which the response is mediated. The effects of injury (fracture of the femur) and the protein content of the diet on the rate of breakdown of plasma albumin in rats was studied using 131I-labelled rat plasma albumin. It was confirmed that the rate of breakdown of albumin was significantly greater when animals were maintained on a high protein diet than when they were deprived of protein. Nevertheless, the catabolic rate of plasma albumin was unaffected by injury in animals fed either a high or a low protein diet. The total plasma protein concentration and the protein and ribonucleic acid content of the livers of animals fed a diet of high protein content was greater than in those animals deprived of protein; none of these levels was affected by injury. It was concluded that although the metabolism of the liver and plasma proteins was affected by diet, they were not involved in the metabolic response to injury, and that the source of the increased nitrogen loss in the urine must have been the carcass. The effect of the level of protein feeding on protein synthesis in the liver was next studied. Since it had previously been shown that the greater part of the protein produced in the liver was synthesised by the microsomes, this fraction was studied in some detail. It was shown that when animals were deprived of dietary protein, the protein, ribonucleic acid and phospholipid phosphorus content of the microsomes was considerably reduced. The incorporation of 14C-leucine in vitro by the rat microsome fraction was greater two hours after feeding casein than following a fifteen-hour fast. In a study of the ribosome aggregates (polysomes) using a sucrose density gradient technique it was shown that there was a greater amount of free ribosomes in the preparation obtained from fasting animals than in the fraction obtained from animals which had been fed casein two hours previously. It was concluded that these results were compatible with the hypothesis that feeding protein led to a release of "messenger" ribonucleic acid from the nucleus which in turn led to an increase in the formation of aggregates of ribosomes and subsequently an increased synthesis of protein. Also in the course of this work, the fractionation of proteins by ion exchange chromatography was investigated, methods of estimating organic nitrogen and protein were reviewed, and an ultraviolet spectrophotometrie procedure for the estimation of ribonucleic acid was devised.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: H N Munro
Keywords: Physiology
Date of Award: 1964
Depositing User: Enlighten Team
Unique ID: glathesis:1964-73962
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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