Intrinsic Factor-mediated Attachment of Vitamin B₁₂ to Brush Borders and Microvillous Membranes of Hamster Intestine

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Abstract

Hamster intrinsic factor (IF) preparations markedly enhanced the uptake of 57cobalt-labeled cyanocobalamin (B12-57Co) by brush borders and microvillous membranes isolated from villous absorptive cells obtained from the distal but not the proximal half of hamster intestine. A similar effect was observed with rat and rabbit IF preparations, but IF preparations obtained from man, dog, and hog were ineffective. After fractionation of hamster IF preparations by gel filtration or ion exchange chromatography, the extent to which each fraction enhanced B12-57Co uptake by brush borders correlated closely with the vitamin B12 binding capacity of the fraction. IF-mediated attachment of B12-57Co to brush borders occurred rapidly, was not diminished by removal of glucose or oxygen from the incubation medium, and was not significantly altered when incubation temperatures were reduced from 37° C to 7° C. Marked reduction in uptake occurred, however, in the absence of divalent cations.

Authors

Robert M. Donaldson Jr., Iain L. Mackenzie, Jerry S. Trier