Formation and utilization of methionine by rat liver cells in culture |
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Authors: | Mary J Wilson Nina V Myasishcheva Gary D Stoner Lionel A Poirier |
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Institution: | (1) Laboratory of Carcinogen Metabolism, National Cancer Institute, 20205 Bethesda, Maryland;(2) Laboratory of Experimental Pathology, National Cancer Institute, 20205 Bethesda, Maryland;(3) Present address: Nutrition and Metabolism Section, Laboratory of Comparative Carcinogenesis, NCI, FCRF, Bldg. 538, 21701 Frederick, MD;(4) Present address: Cancer Research Center of the Academy of Medical Sciences, Moscow, USSR;(5) Present address: Department of Pathology, Medical College of Ohio, 43699 Toledo, OH |
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Abstract: | Summary The enzymeN
5-methyltetrahydrofolate: homocysteine methyltransferase (methionine synthetase) catalyzes the synthesis of methionine from
homocysteine. Methylcobalamin is a cofactor for the reaction. The effects of methionine deprivation and methylcobalamin supplementation
on the growth of normal and transformed rat liver epithelial cell lines were determined using growth constants to quantitate
cell proliferation. No marked specific requirement by the transformed cell lines for methionine relative to leucine was observed.
A sigmoidal relationship, however, was found to exist between growth constants and the logarithms of the amino acid concentrations
for both normal and transformed cells. Methylcobalamin stimulated the growth rates of the normal and transformed liver cells
in methionine-deficient, homocysteine-containing medium. Growth on methionine was not increased by the addition of methylcobalamin.
The growth constants for two normal, two spontaneously transformed, one chemically transformed, and one tumor cell line grown
in medium in which methionine was replaced by homocysteine were found to be proportional to the level of methionine synthetase.
The results demonstrate the utility of growth quantitation to study the methionine dependency of transformed cells.
Presented in part at the Conference on Differentiation and Carcinogenesis in Liver Cell Cultures sponsored by the New York
Academy of Sciences, October 11, 1979 (see reference 1). |
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Keywords: | liver cells methionine methionine synthetase growth constants methylcobalamin |
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