Intrinsic factor-mediated radio-B12 uptake in sequential incubation studies using everted sacs of guinea pig small intestine: evidence that IF in not absorbed into the intestinal cell.

Abstract

SummarySequential incubation studies using everted sacs of guinea pig small intestine and vitamin B12 labeled with two different isotopes of cobalt, 60Co and 57Co, showed that IF-saturated with B12, could effect specific attachment of the complex to distal sacs. In a subsequent incubation IF could: (i) mediate in specific fashion (not exchange) the uptake of additional B12, (ii) interact with IF-“blocking” antibody, and (iii) be partially dissociated by EDTA from the sac (in a form biologically active for this system and retaining specificity of activity) leaving its B12 attached to the mucosa. These results were interpreted to indicate that, in this experimental system, IF is not absorbed into the intestinal cell during the B12 uptake that is mediated by intrinsic factor.