Pyridoxal phosphate in lymphocytes, polymorphonuclear leukocytes, and platelets in Down’s syndrome

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Abstract
Pyridoxal phosphate concentrations were measured in platelets and in lymphocytes and polymorphonuclear leukocytes separated on glass bead columns. Platelet pyridoxal phosphate was significantly (P < 0.05) decreased in Down’s syndrome (0.269 ng/l08 platelets) compared with normal (0.321) and mentally retarded controls (0.328). Lymphocyte pyridoxal phosphate concentrations were not significantly different between the groups (8.8, 8.4, and 7.8 ng/l08 cells). Pyridoxal phosphate concentrations in polymorphonuclear leukocytes were two- to threefold higher than in the lymphocytes in all groups. This may be due primarily to the larger size of the polymorphonuclear leukocytes. However, a slight increase in the pyridoxal phosphate/protein ratio suggests that metabolic differences may also be involved. Pyridoxal phosphate concentrations were significantly (P < 0.05) reduced in the polymorphonuclear leukocyte fraction in Down’s syndrome (18.1 ng/l08 cells) compared with normal (22.9) and mentally retarded controls (22.1). It is postulated that pyridoxal phosphate turnover is increased in these cells in Down’s syndrome and that EDTA exposure during cell fractionation inhibits the synthesis of pyridoxal phosphate producing a net loss in the Down’s syndrome cells.