Abstract
Summary
Within 24 hr after intravenous administration of isotopic 25-hydroxyvitamin D3 to three normal adults for kinetic studies, one-third of the radioactivity was secreted into the lumen of the duodenum, probably with the bile. The subsequent intestinal reabsorption of over 85% of secreted radioactivity suggests that this major metabolite of vitamin D has a hitherto unrecognized enterohepatic circulation.
Our observation of a dynamic hepatic secretion and intestinal reabsorption of radioactivity administered as 3H-labeled 25-hydroxyvitamin D3 to vitamin D-replete man is indicative of an enterohepatic circulation that may be of physiologic importance. It is conceivable that interruption in the recycling of 25-OH-D3 may be an important mechanism of acquired deficiency of vitamin D in gastrointestinal disease.
This investigation was supported in part by Research Grants AM-69-2168, RR 585, and AM-6908 from the National Institutes of Health, Public Health Service. We gratefully acknowledge the technical assistance of Jane Bailey, Pamela A. Bonnes, Diane J. Brinck, Mary C. Matthusen, Garry V. Mussmann, and the nursing staffs of the Russell M. Wilder Clinical Study Unit and the Gastroenterology Unit.
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