Increased methionine synthetase activity in zinc-deficient rat liver |
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Authors: | T Tamura L L Kaiser J E Watson C H Halsted L S Hurley E L Stokstad |
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Affiliation: | 1. Department of Anthropology, McMaster University, 1280 Main St. West, L8S 4L8 Hamilton, Ontario, Canada;2. School of Geography and Earth Sciences, McMaster University, 1280 Main St. West, L8S 4L8 Hamilton, Ontario, Canada |
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Abstract: | To study the effect of zinc deficiency on folate metabolism, three groups of male Sprague-Dawley rats (zinc deficient (ZD), restricted-fed (RF + Zn), and ad libitum-fed control (control] were given a semipurified 25% egg white protein diet. The ZD group received less than 10.3 nmol zinc/g of diet, while the RF + Zn and control groups were given 1620 nmol zinc/g of diet. After 6-7 weeks of feeding, severe zinc deficiency developed in ZD rats. Hepatic methionine synthetase activity was increased in the ZD group compared to both the RF + Zn and control groups, but hepatic 5,10-CH2-H4folate reductase activity was similar in all groups. This increased methionine synthetase activity found in zinc-deficient rats might induce secondary alterations in folate metabolism. These changes include significantly lowered plasma folate levels, decreased 5-CH3-H4folate in liver, and increased rates of histidine and formate oxidation. The latter two findings suggest that the available non-5-CH3-H4folate is increased in zinc deficiency. |
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