Abnormal tryptophan metabolism in pregnancy and with the oral contraceptive pill. II. Relative levels of vitamin B6-vitamers in cord and maternal blood

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Abstract
Paired samples of maternal and cord blood plasma were analyzed for the three vitamin B6-vitamers and for total vitamin B6 content. Also, the erythrocytes from the same blood samples were analyzed for oxalacetic and pyruvic aminotransferase activity. Levels of vitamin B6-vitamers in plasma and of erythrocyte aminotransferase activity were at least twice as high in cord blood as in maternal blood. The compartmentalization of vitamin B6 in the fetus may have been due to an active placental transport mechanism, or may have reflected increased numbers of binding sites in fetal tissues due to increased levels of pyridoxine-requiring enzymes. Either of these mechanisms might result in partial depletion of the mother-host for vitamin B6. The findings also serve to partially explain the high incidence of abnormal tryptophan load tests in pregnancy.