THE PIG IS AN APPROPRIATE MODEL FOR HUMAN BIOTIN CATABOLISM AS JUDGEDBY THE URINARY METABOLITE PROFILE OF RADIOISOTOPE-LABELED BIOTIN

Because the rat model of biotin deficiency and biotin metabolism has i mportant limitations, we sought to determine whether the urinary profi le of biotin and its metabolites in pigs is similar to that in humans. Biotin labeled with either H-3 On the side chain or C-14 On the ureid o ring was administered intravenously to 2-mo-old male pigs. Biotin an d its metabolites were identified and quantified by HPLC and radiometr ic flow detection. At tracer doses of [H-3]biotin, 12 +/- 6% (mean +/- SD, n = 3) of total administered radioactivity was excreted within 72 h; at a physiologic dose of [C-14]biotin, 47 +/- 2% (n = 5) of the ad ministered radioactivity was excreted within 72 h. Biotin was the majo r form excreted, as it was in humans. Substantial amounts of bisnorbio tin and biotin sulfoxide, two known biotin metabolites, were also excr eted. Bisnorbiotin methyl ketone and biotin sulfone, two biotin metabo lites recently identified in human urine, were also present in pig uri ne. This study provides evidence that biotin metabolism in pigs resemb les that in humans.