The role of the pancreas in vitamin B 12 absorption: studies of vitamin B 12 absorption in partially pancreatectomized rats.

The effect of partial pancreatectomy (80-90%) on vitamin B(12) absorption was studied in the rat. The absorption of 5 ng of (57)Co-labeled vitamin B(12) was significantly reduced from 70 +/-2.5% (mean +/-SE) in control and sham-operated rats to 32 +/-2.6% in partially pancreatectomized rats. Hog pancreatic extract (0.17 g/kg) improved vitamin B(12) absorption from 30.0 to 61.0% in partially pancreatectomized rats but did not alter vitamin B(12) absorption in control rats. Chloramphenicol did not enhance vitamin B(12) absorption in partially pancreatectomized rats with pancreatic extract-improved vitamin B(12) malabsorption. The partially pancreatectomized rats with pancreatic extract-improved vitamin B(12) malabsorption were sacrificed and the stomach and small bowel studied in vitro to further define the pathogenesis of the vitamin B(12) malabsorption. Rat gastric intrinsic factor stimulated vitamin B(12) uptake by intestinal sacs prepared from partially pancreatectomized rats 3.1-fold. Gastric intrinsic factor prepared from partially pancreatectomized rats was as effective in promoting vitamin B(12) uptake by rat intestinal sacs as intrinsic factor prepared from control rats. These data indicate that partially pancreatectomized rats develop an abnormality in the absorption of labeled vitamin B(12) which can be corrected by pancreatic extract. The vitamin B(12) malabsorption is due to neither an alteration in gastric intrinsic factor activity nor an impairment of the intrinsic factor-vitamin B(12) receptor in the intestine. It is suggested that in the partially pancreatectomized rats the intrinsic factor-vitamin B(12) complex exists in a form which is not available for absorption.