Human Intestine INHIBITED COBALAMIN ABSORPTION IN EXOCRINE PANCREATIC DYSFUNCTION

upper gastrointestinal tract are essential determining factors for transport and absorption of cobalamin in man. Jejunal fluid was aspirated from healthy human volunteers after administration of cyano[57Co]cobalamin preparations. Immunochemical analysis of the aspirates demonstrated that all isotopic vitamin was transferred to a protein that is identical to the gastric intrinsic factor in terms of molecular mass (57,500), ionic nature (mean pI, 5.09), and reactivity with antiintrinsic factor sera. However, in the aspirates from patients with exocrine pancreatic dysfunction the vitamin was found to be coupled >60% to a protein identical to R proteins in terms of molecular mass (125,000), ionic nature (mean pI, 3.51), and reactivity with antiR protein and anti-intrinsic factor sera. The preferential transfer of cobalamin to R proteins in the patients and to intrinsic factor in healthy subjects was associated, respectively, with low and normal levels ofpancreatic enzymes in the intestine and these in turn were paralleled respectively by impaired and normal ileal absorption of cobalamin. These findings confirm the suggestion that the formation of unabsorbable cobalamin complexes may be the reason of impaired vitamin absorption in exocrine pancreatic insufficiency. This paper was presented in part at the 3rd European Symposium on Vitamin B12 and Intrinsic Factor, March 1979, Zurich, Switzerland. Dr. Marcoullis is a visiting professor of medicine under the auspices of Institut National de la Sante et de la Recherch6 Medicale at the University of Nancy. The permanent address for Dr. Marcoullis and Ms. Jimenez is Department of Medicine, Veterans Administration Hospital, Brooklyn, N. Y. Received for publication 2 November 1979 and in revised form 19 May 1980. 430 Observations made with other selected patients demonstrate: (a) that decreased enzyme activity and nondegradation of R proteins may also be due to nonactivation ofpancreatic zymogens in an acidic pH ofthe intestinal juice and; (b) that in the absence of an acidic environment in gastric juice the vitamin transported to the jejunum couples to intrinsic factor when pancreatic function is normal, and to intrinsic factor and R protein in exocrine pancreatic insufficiency. The observations made with these selected patients may explain why not all patients with exocrine pancreatic insufficiency develop impaired cobalamin absorption, and also why the malabsorption is corrected by the administration of bicarbonate in certain patients.