Relative Activities of Some Metabolites and Analogs of Cholecalciferol in Stimulation of Tibia Ash Weight in Chicks Otherwise Deprived of Vitamin D

Nine metabolites and analogs of cholecalciferol (CC) were tested for ability to increase tibia ash weight in chicks otherwise deprived of vitamin D. All of the compounds promoted bone mineralization in a linear log dose-response relationship. The maximal response obtained for any compound was an approximate doubling in bone ash weight compared to vehicle-treated controls. Relative potencies, based upon the calculated ash weight doubling dose, were as follows: 1 alpha, 25-(OH)2-CC = 1 alpha-OH-CC greater than CC greater than 25-OH-CC greater than 24R, 25-(OH)2-CC = 1 alpha,24R, 25-(OH)3- CC greater than 5,6-trans-25-OH-CC greater than 1 alpha, 24S, 25- (OH)3-CC greater than 5,6-trans-CC greater than 24S, 25-(OH)2-CC.