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Bioavailability of Vitamin B-6 in Pregnant Rats^1,2,3,

Department of Foods and Nutrition, Purdue University, West Lafayette, IN 47907

The cause for reduced plasma pyridoxal phosphate (PLP) concentration during pregnancy is not well understood. In this study, nonpregnant (control) and pregnant rats were gavaged with [³H]pyridoxine for assessment of the intestinal absorption, tissue distribution, metabolic utilization and urinary excretion of the vitamin. In addition, plasma PLP and pyridoxal levels and erythrocyte aspartate aminotransferase (EAST) activity were measured. There was 50% lower plasma PLP concentration and 50% greater EAST activity in the pregnant rats and no difference in the stimulation of EAST with exogenous PLP. There was no difference in the intestinal absorption, hepatic uptake and retention or urinary excretion of the radioisotope. Less than 3% of the oral dose was detected in fetal/uterine tissue of the pregnant rats. Results of this study indicate that reduced plasma PLP concentration during pregnancy is not a result of diminished total vitamin B-6 body pools or fetal sequestration of vitamin B-6. Low plasma PLP during pregnancy may be a result of altered distribution of PLP between the plasma and erythrocytes.

KEY WORDS: • pregnancy • vitamin B-6 • rats • bioavailability

¹ A preliminary report was presented at the Annual Meeting of the Federation of American Societies for Experimental Biology, April 1992, Anaheim, CA [Wang, J. W. & Trumbo, P. R. (1992) The bioavailability of vitamin B-6 during pregnancy in rats. FASEB J. 4: A1372 (abs. 2526)].

² Supported in part by USDA Cooperative State Research Service National Research Initiative Competitive Grants Program 91-37200-6274.

³ Journal Paper No. 13331 of the Agricultural Experiment Station, Purdue University, West Lafayette, IN 47907.

⁴ To whom correspondence should be addressed.

Manuscript received 26 February 1992. Revision accepted 11 May 1992.