Changes in membrane protein and carbohydrate associated with erythrocyte aging

Baxter, Allan (1975) Changes in membrane protein and carbohydrate associated with erythrocyte aging. PhD thesis, University of Glasgow.

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Abstract

The in vivo aging of human erythrocytes is accompanied by a progressive increase in red cell specific gravity. Use has been made of this fact to obtain erythrocytes of different in vivo age by ultracentrifugation of washed red cells on discontinuous density gradients of iso-osmotic bovine albumin. The rod cells of two individuals exhibited an age-related decrease of about 20% in the cell surface N-acetylneuraminic acid. This change was shown to be due to a generalised loss of sialic acid from all of the major membrane sialoglycoproteins. Membranes were isolated from cell fractions of different age and subjected to carbohydrate analysis. The finding for N-acetyl-neuraminic acid was confirmed and additional decreases were observed in galactose, glucose, N-acetylgalactosamine and N-acetylglucosamine of old cell membranes. While some of these decreases are probably attributable to glycolipid losses, which are known to accompany aging, part of the galactose/N-acetyl-galactosamine depletion has been related, to the sialoglyeoproteins of the membrane. Changes in cell surface carbohydrates have also been detected by studying the relative susceptibility to agglutination of erythrocytes of different in vivo age using a number of agglutinins. Old cells were consistently more agglutinable and in the case of one of these agglutinins, wheat-germ agglutinin, the increased agglutinability was shown not to be due to an increase in the number of lectin binding sites, nor to any marked redistribution of intramembranons particles of old cells. More-over, the interaction of in vivo aged cells with agglutinins could be mimicked by neuraminidase or trypsin treated unfractionated erythrocytes. Analysis of the major protein components of the membranes of fractionated cells by SDS-polyacrylamide gel electrophoresis indicated that aging was accompanied by the appearance of two new polypeptides of approximate molecular weights 63,000 and 25,000, with probable degradation of component 3- an extracellular surface membrane glycoprotein. Treatment of intact red cells with a variety of proteolytic enzymes produced n new component of molecular weight 61-63,000 and also degraded component 3 and the membrane sialoglycoproteins. Since trypsin treatment of erythrocytes produced cells which mimicked vivo aged cells in their behaviour with agglutinins, the findings presented here are consistent with erythrocyte in vivo aging being accompanied by proteolysis of the external membrane surface of the red cell. The relevance of these observations to the sequestration of senescent erythrocytes is discussed.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J G Becley
Keywords: Molecular biology
Date of Award: 1975
Depositing User: Enlighten Team
Unique ID: glathesis:1975-72845
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 11 Jun 2019 11:06
URI: http://theses.gla.ac.uk/id/eprint/72845

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