Turnover of the plasma-membrane and microsomal proteins of rat liver containing primary hepatoma nodules

Narayan, K A; Chandrasekhara, N.

doi:10.1042/bj1240953

Cited by 6 publications

(1 citation statement)

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“…These differences may reflect the dependence from environmental factors as blood supply or immunological defence which may change with the growth of the tumor. Our observations fit well with studies reporting variable changes of the half-lives in IWO of microsomal proteins of the Morris hepatomas 7800 and 9618A [32] and a doubled halflife of microsomal and bile-front proteins of 2-Nfluorenyl-acetamide-induced hepatomas compared to normal liver [33]. The alterations in the protein catabolism of the hepatomas correspond with the heterogeneity of other biochemical parameters such as the metabolism of L-fucose, D-galactose and N-acetylneuraminic acid [34 -361.…”

Section: Discussionsupporting

confidence: 79%

Protein Degradation in the Plasma Membrane of Regenerating Liver and Morris Hepatomas

Tauber

Reutter

1978

Eur J Biochem

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2. Autoradiographic analysis of the decay of radioactivity in plasma membrane polypeptides indicated that the substantially decreased breakdown of proteins is not restricted to single polypeptides of the plasma membrane. No significant differences in the relative degradation rates of individual plasma membrane proteins from regenerating liver could be found. In normal liver, however, distinct differences were observed.3. In Morris hepatomas half-lives varied with age and type of the tumor. In the hepatoma 3924A degradation was decreased substantially, whereas in the more rapidly growing hepatoma 7777 no significant change of the half-lives could be found. As to the hepatoma 9121, 20 days after inoculation protein catabolism was slightly elevated, but was lowered when determined in 27-day-old tumors.4. From these results it can be concluded that the prolongation of the half-life of plasma membrane proteins is a characteristic feature of regenerating liver. It is likely that in Morris hepatomas 7777, 9121 and 3924A the regulation of the degradation of these membrane constituents is impaired.During increased proliferation cellular adhesion and cell-to-cell interaction are altered [1,2]. The regulation of these biological properties is closely associated with the plasma membrane as the site of hormone receptors, transplantation antigens and transport proteins. Moreover, the high rate of cell division requires more plasma membrane material. This supply can be provided by an increased rate of synthesis or by a restricted rate of degradation, beEnzymes. 5'-Nucleotidase or 5'-ribonucleotide phosphohydrolase (EC 3.1.3.5); succinate dehydrogenase or succinate: 2-(piodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium oxidoreductase (EC 1.3.99.1) ; glucose-6-phosphatase or ~-glucose-6-phosphate phosphohydrolase (EC 3.1.3.9); Xg2+/Ca2+ ATPase and Na+/K+ ATPase (EC 3.6.1.3).cause it has been pointed out in a number of recent reviews, that the pool of intracellular proteins is controlled by anabolic or catabolic processes or both [3 -61. As has been demonstrated for total cell homogenate [7] a decreased rate of protein breakdown is responsible, at least partly, for the net protein gain in regenerating rat liver. With respect to the role of the cell surface in growth control, the degradation of plasma membrane proteins was investigated in the present paper. Three different states of differentiation were investigated : the regenerating liver after partial hepatectomy as an example of controlled rapid growth, the Morris hepatomas 7777, 3924A and 9121 as a model of an uncontrolled proliferating tissue and normal liver as control.

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Section: Discussionsupporting

confidence: 79%