Leukocyte Pyridoxal Phosphate and Alkaline Phosphatase in Down's Syndrome and Other Retardates

Abstract

Leukocyte pyridoxal phosphate (PALP) and alkaline phosphatase levels were measured in five groups of institutionalized retardates and in normal controls before and after supplementation with 10 mg pyridoxine-HCl/day for 7 days. Serum pyridoxal was measured after supplementation. The trisomic Down's syndrome subjects tended to have the lowest PALP and highest alkaline phosphatase levels. There was a small, significant (P < 0.05) negative correlation between leukocyte PALP and alkaline phosphatase both before (r = –0.38) and after (r = –0.31) supplementation. There was a significant (P < 0.01) positive partial correlation (r = 0.44) between serum pyridoxal and leukocyte PALP after supplementation. The partial correlation (r = 0.06) between serum pyridoxal and leukocyte alkaline phosphatase was negligible. It is concluded that both serum pyridoxal and leukocyte alkaline phosphatase may be significant factors in determining leukocyte PALP levels. In addition, the possibility of interference from alkaline phosphatase should be considered in any measurement of PALP levels in a system containing this enzyme.