Analysis of corrinoids in ovine tissues
Kelly, RJ, Gruner, TM, Furlong, JM & Sykes, AR 2006, 'Analysis of corrindoids in ovine tissues', Biomedical Chromatography, vol. 20, no. 8, pp. 806-814.
The publisher's version of this article is available at http://dx.doi.org/10.1002/bmc.604
Corrinoids from various ovine tissue samples (liver, blood, small intestinal fluid and faeces) were analysed using a combination of high-performance liquid chromatography (HPLC) and a radioisotope dilution assay (RIDA) to estimate the distribution of corrinoids - the cobalamins hydroxocobalamin (OH-cbl), methylcobalamin (me-cbl) and 5-deoxyadenosylcobalamin (ado-cbl), and cobalamin analogues - in these tissues. Samples were taken from either cobalt-deficient or cobalt-replete ewes, and ruminant and pre-ruminant lambs. In liver, ado-cbl predominated, followed by analogues, OH-cbl and me-cbl. Supplementation with either cobalt (ruminant) or vitamin B12 injections (pre-ruminant) increased the amount of ado-cbl and decreased analogues. In blood, OH-cbl predominated, followed by ado-cbl, analogues and me-cbl, respectively. In small intestinal fluid, the distribution from largest to smallest percentage was analogues, ado-cbl, OH-cbl and me-cbl. In faeces, analogues constituted the greatest proportion, followed by OH-cbl, ado-cbl and me-cbl, respectively. Owing to the small sample sizes only cautionary interpretations can be made. In contrast to humans, where me-cbl constitutes the highest proportion of corrinoids in plasma and ado-cbl in the liver, in sheep the amount of ado-cbl was consistently higher than me-cbl in all tissues. This may be due to the higher metabolic need of sheep for ado-cbl due to gluconeogenesis. Analogues and OH-cbl were found in each tissue, contrary to previous postulations. The much higher amount of vitamin B12 in small intestinal fluid compared with faeces indicates that a large proportion of the vitamin is absorbed by the gastro-intestinal tract.