QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Leibman, D. Articles by Smolen, A. Search for Related Content PubMed PubMed Citation Articles by Leibman, D. Articles by Smolen, A.

Vitamin B-6 Metabolic Enzymes in Blood and Placenta of Pregnant Mice¹

David Leibman^*, David Furth-Walker^* and Andrew Smolen^*,,2

^* Institute for Behavioral Genetics Drug Abuse Research Center, University of Colorado, Boulder, CO 80309-0447

Plasma pyridoxal 5'-phosphate (PLP) concentrations decrease 50% in pregnant mice and erythrocyte PLP levels increase threefold over non-pregnant levels. These studies were designed to determine whether changes in the enzymes involved in synthesis and degradation of PLP in blood are altered during pregnancy. We measured net synthesis of PLP in erythrocytes and the activity of enzymes involved in the regulation of plasma and erythrocyte PLP concentrations: erythrocyte pyridoxal kinase (PLK) and neutral phosphatase, and plasma and tissue alkaline phosphatase (ALP). Net synthesis of PLP and activities of erythrocyte PLK and neutral phosphatase in erythrocytes remained unchanged during pregnancy. We were unable to detect any dephosphorylation of PLP in erythrocytes of pregnant or nonpregnant mice. Mouse erythrocytes were devoid of ALP activity; neutral phosphatase was inactive with PLP and PLP was an uncompetitive inhibitor of the enzyme. Plasma ALP activity decreased 50% in the pregnant mice; therefore, it likely does not participate in the reduction of plasma PLP levels during pregnancy. Placenta had high levels of PLP-phosphatase activity (ALP) and, if it is active as an ectoenzyme in this tissue as it is in others, it may be the most important mediator of plasma PLP levels in pregnancy.

KEY WORDS: • pregnancy • vitamin B-6 • pyridoxal 5'-phosphate • alkaline phosphatase • mice

¹ Supported by grants from the National Institute of Child Health and Human Development, HD 21709, National Institute on Alcohol Abuse and Alcoholism, AA 07464 and National Institute on Drug Abuse, DA 05131.

² To whom correspondence should be sent.

Manuscript received 31 July 1989. Revision accepted 18 October 1989.