Metabolism of Vitamin D in the Chick

Abstract

Summary

The metabolism of large (hypercalcemic) dosages of vitamins D₂ and D₃ has been studied in the chick. The chick evidently does not absorb vitamin D₂ as well as it does vitamin D₃, at least in the doses given; a larger proportion of it is found in the feces, and less is found in the carcasses. The amounts of vitamin D₃ found in carcasses and feces account for all of the dosage given, but about 35% of the vitamin D₂ cannot be accounted for. Analysis of the data indicated that there are two phases of inactivation of the vitamins. In the first both are inactivated at about the same rate, but in the second phase the rate of destruction of vitamin D₂ is about 50% greater. The generally more rapid inactivation of vitamin D₂ in the tissues may have a bearing on the fact that it is less effective in the chick than is vitamin D₃.