Bone Resorbing Activity of Vitamin D Metabolites and Congenersin Vitro:Influence of Hydroxy1 Substituents in the A Ring

Publisher Website
Google Scholar
Abstract
The vitamin D3 derivatives, 1.alpha.-hydroxyvitamin D3, 1.alpha.-hydroxy-3-deoxyvitamin D3, 5,6-trans-vitamin D3 and 5,6-trans-25-hydroxyvitamin D3 were tested for bone resorbing activity in vitro using fetal rat bones. 1.alpha.-Hydroxy-3-deoxyvitamin D3 and 5,6-trans-vitamin D3 were inactive at concentrations as high as 10-6M. 1.alpha.-Hydroxyvitamin D3 had significant effects on mineral and matrix resorption at concentrations of 2.5 .times. 10-8M and above, and was 2-3 orders of magnitude less potent than 1,25-dihydroxyvitamin D3 in this system. A concentration of 2.5 .times. 10-7M of 5,6-trans-25-hydroxyvitamin D3 was required to stimulate 45Ca release. In the vitamin D3 series of compounds the presence of only 1 hydroxyl group in the molecule in either the 1.alpha. or the 3.beta. position in the A ring results in a compound with very limited or no direct effects on bone. The direct effects of vitamin D3 congeners on bone resorption do not require the presence of a 25-hydroxy group but their activity is markedly enhanced by the 25-hydroxy group.

This publication has 1 reference indexed in Scilit: