Studies of Calcium and Phosphorus Metabolism in the Chick: II. Relative Antirachitic Effectiveness of Vitamins D2 and D3 and Dihydrotachysterol Administered Parenterally

Abstract

The relative effectiveness of vitamin D2 and D3 and dihydrotachysterol when administered parenterally to the chick in propylene glycol and corn oil has been studied. Rather definite requirements have been established for the different preparations by the several routes of administration and are presented in the form of a table. Although the weekly oral requirements (as defined herein) of the three preparations administered in oil are: vitamin D3, 24 units; vitamin D2, 850 units; and dihydrotachysterol, 6 units (i.e., in the proportions of 1:35:0.25), the intramuscular requirements in propylene glycol (in the same order) are 9,150, and 6 units (i.e., in the proportions of 1:16:0.7) and the intravenous requirements (in the same order) are 9,110, and 10 units (i.e., in the proportions of 1:12:1.1). Thus although dihydrotachysterol is 300% more effective than vitamin D3 by the oral route, it averages only about 20% more effective by the parenteral routes. The data on relative oral and parenteral utilization of vitamins D2 and D3 indicate that the latter is somewhat better absorbed from the digestive tract.