The Inhibitory Effect of Bile on the Binding of Vitamin B₁₂ to Intrinsic Factor: An in Vivo Study in Rats

Abstract

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 < 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<0.001).

Key Words:

• Bile
• intrinsic factor
• rats
• vitamin B₁₂