Uptake of Protein Bound Vitamin B 12 by Canine Organs 1

Abstract

Summary

The isolated, perfused, canine spleen and heart took up 40-50% of vitamin B-12 labeled with ⁵⁷Co and bound to canine transcobalamin II (TC II). Other proteins that bind vitamin B-12 depressed uptake. In contrast to previous experience with the liver, binding to TC II did not enhance uptake as compared to uptake of free ⁵⁷CoB₁₂. In contrast to previous experience with the kidney, very high uptake of free B-12 was not observed. The transport of B-12 into whole organs differed in some aspects from transport into suspension of cells. Possibly the ability of the organs to produce transport proteins accounted for these differences.