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Tissue distribution of oral vitamin B12 is influenced by B12 status and B12 form: an experimental study in rats

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Purpose Hydroxocobalamin (HOCbl) is the dominating Cbl form in food, whereas cyanocobalamin (CNCbl) is common in vitamin pills and oral supplements. This study compares single-dose absorption and distribution of oral HO[Co-57] Cbl and CN[Co-57] Cbl in Cbl-deficient and normal rats.

Methods Male Wistar rats (7 weeks) were fed a 14-day diet with (n = 15) or without (n = 15) Cbl. We compared the uptakes of HO[Co-57] Cbl (free or bound to bovine transcobalamin) and free CN[Co-57] Cbl administered by gastric gavage (n = 5 in each diet group). Rats were sacrificed after 24 h. Blood, liver, kidney, brain, heart, spleen, intestines, skeletal muscle, 24-h urine and faeces were collected, and the content of [Co-57] Cbl was measured. Endogenous Cbl in tissues and plasma was analysed by routine methods.

Results Mean endogenous plasma-Cbl was sevenfold lower in deficient vs. normal rats (190 vs. 1330 pmol/L, p <0.0001). Cbl depletion increased endogenous Cbl ratios (tissue/plasma = k(in)/k(out)) in all organs except for the kidney, where the ratio decreased considerably. Twenty-four-hour accumulation of labelled Cbl showed that HOCbl > CNCbl (liver) and CNCbl > HOCbl (brain, muscle and plasma).

Conclusions The Cbl status of rats and the administered Cbl form influence 24-h Cbl accumulation in tissues and plasma.

Original languageEnglish
Article number4
JournalEuropean Journal of Nutrition
Pages (from-to)1459-1469
Number of pages11
Publication statusPublished - Jun 2018

    Research areas

  • Cobalamin deficiency, Cyanocobalamin, Hydroxocobalamin, Intestinal absorption, Kinetic modelling

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