Vitamin E. Deficiency increases the synthesis of platelet-activating factor (PAF) in rat polymorphonuclear leucocytes |
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Authors: | Kenji Fukuzawa Yasuhiro Kurotori Akira Tokumura Hiroaki Tsukatani |
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Affiliation: | (1) Faculty of Pharmaceutical Sciences, Tokushima University, 1-78 Shomachi, 770 Tokushima, Japan |
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Abstract: | Vitamin E deficiency was found to stimulate FMLP (N-formyl-L-methionyl-L-leucyl-L-phenylalanine)-induced biosynthesis of PAF
(1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in polymorphonuclear leucocytes (PMN) from rat peritoneum. In three separate experiments each,
the amounts of PAF synthesized during 6min and 12 min incubation of PMN cells from control, vitamin E-supplemented, and vitamin
E-deficient rats were 129–240, 131–227 and 248–354 pmol/106 cells, respectively. The activity of the acetyl-transferase, which transfers the acetyl moiety of 3H]acetyl-CoA to 2-lysoPAF (1-O-alkyl-sn-glycero-3-phosphocholine) to form 3H]PAF, was higher in PMN homogenates from vitamin E-deficient rats (2.28±0.07 nmol/min/mg protein) than in those from E-supplemented
rats (1.06±0.10 nmol/min/mg protein). However, there was no difference between the two groups in the activity of acetylhydrolase
(4.26±0.71 and 4.26±0.06 nmol/min/mg protein, respectively), measured as degradation of 3H]PAF to 3H]lysoPAF.In vitro addition of α-tocopherol did not inhibit the increased activity of acetyl-transferase in vitamin E-deficient rats, in-dicating
that the enzyme in vitamin E-supplemented rats was not directly inhibited by α-tocopherol. The acetyltransferases of the two
groups showed similar Km values for acetyl-CoA, but different Vmax values (225 μM and 6.4 nmol/min/mg protein in vitamin E-deficient
rats, and 216 μM and 3.6 nmol/min/mg protein in vitamin E-supplemented rats), suggesting that the enzyme was not activated
but increased in amount in vitamin E deficiency. |
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