Absorption of food cobalamins assessed by the double-isotope method in healthy volunteers and in patients with chronic diarrhoea.
To make a food preparation containing radioactively labelled cobalamins, rabbits were given repeated injections with 57Co-labelled cyanocobalamin. The liver was removed, homogenized, and fried for 1 min or boiled for 30 min. Of the radioactivity in the fried homogenate 41.7% was recovered in the centrifuged supernatant compared with 50.8% in the boiled homogenate. The radioactivity in the supernatants had a molecular size close to that of free 57Co-labelled cyanocobalamin. Forty-two per cent of the radioactivity in the whole homogenate had been incorporated into 5-deoxyadenosyl-, 10% into methyl-, and 16.5% into hydroxy-cobalamin. To assess the validity of a double-isotope method for measuring the intestinal absorption of doses of the 57Co-labelled liver cobalamins, 51CrCl3 was used as a non-absorbable marker. In 14 healthy volunteers the correlation coefficient between the absorption measured by the double-isotope technique and the faecal excretion test was highly significant (r = 0.96, p less than 0.005), and there was only a small variation in the 57Co/51Cr ratio in successive stool collections. In 11 patients with chronic diarrhoea there was a significant correlation between the absorption measured by the double-isotope technique and the faecal excretion test (r = 0.92, p less than 0.005), but in some patients there was considerable variation in the 57Co/51Cr ratio in successive stool collections.
D000328:Adult; D000368:Aged; D000818:Animals; D002850:Chromatography, Gel; D002908:Chronic Disease; D003037:Cobalt Radioisotopes; D003937:Diagnosis, Differential; D003967:Diarrhea / Q000175:diagnosis / Q000378:metabolism*; D005502:Food; D006801:Humans; D007408:Intestinal Absorption; D007437:Intrinsic Factor / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008875:Middle Aged; D008970:Molecular Weight; D011817:Rabbits; D014155:Transcobalamins / Q000378:metabolism; D014805:Vitamin B 12 / Q000008:administration & dosage / Q000378:metabolism*
D003037:Cobalt Radioisotopes; D014155:Transcobalamins; D007437:Intrinsic Factor; D014805:Vitamin B 12