Effect of pancreatic extracts on the faecal excretion and on the serum concentration of cobalamin and cobalamin analogues in cystic fibrosis.

A malabsorption of crystalline labelled cobalamin is observed in 100% of cystic fibrosis patients. Using radioisotope dilution assays and molecular sieve gel chromatography, we determined the serum concentration and the faecal excretion of cobalamin and cobalamin analogues in nine cystic fibrosis children before and after 4 days' interruption of pancreatic extract treatment. On chromatography, the unsaturated cobalamin binders of the faecal extracts eluted in two positions with molecular masses of 44 300 and 20 300, corresponding mostly to partially degraded R binders. The amounts of the less degraded form of R binder (molecular mass 44 300) increased significantly after interruption of the treatment. The cobalamin concentration in the serum remained normal after interruption of the treatment but the analogue concentrations in the serum decreased and faecal excretion of cobalamin and analogues increased significantly. These results allowed us to suggest that (1) pancreatic insufficiency in cystic fibrosis is responsible for a decrease in the absorption of digestive analogues induced by a defective degradation of R binders, and (2) cobalamin analogues have a short half-life in blood.