The inhibitory effect of bile on the binding of vitamin B12 to intrinsic factor. An in vivo study in rats.

To investigate whether bile reduces the amount of vitamin B12 bound by intrinsic factor (IF) in the intestinal juice in vivo, choledochocolic fistulae were made in 9 rats, and 10 rats were sham-operated. Small-intestinal juice was collected 1 h after gastric instillation of 57CoB12. The percentage of 57CoB12 bound by IF in the intestinal juice was markedly increased in fistula rats (median, 86%; range, 75-91%) as compared with sham-operated rats (35%; 12-50%) (p less than 0.001). In a second experiment we investigated whether bile enhances the intestinal uptake of the IF-B12 complex. Aliquots of the radioactive intestinal juice collected from the sham- and fistula-operated rats were separately instilled into tied intestinal loops created in 19 rats. The percentage of the instilled radioactivity taken up per 10 cm of the loop was significantly higher when juice from fistula-operated rats was instilled (median, 12.4; range, 4.3-18.7) than when juice from sham-operated rats was instilled (3.3; 1.4-6.2) (p less than 0.001).