Biological Activity of 1,24(R)-Dihydroxyvitamin 3 and 1,24(S)-Dihydroxyvitamin D 3 in the Rat 1

Abstract

The activities of 1,24(R)-dihydroxyvitamin D₃ and 1,24(S)-dihydroxyvitamin D₃ have been compared with that of 1,25-dihydroxyvitamin D₃ in the stimulation of intestinal calcium transport, mobilization of bone calcium, elevation of serum inorganic phosphorus concentration, and in healing rickets in vitamin D-deficient rats. The 1α-hydroxyvitamin D₃ was also compared with the 1,24-dihydroxyvitamin D₃ compounds in antirachitic activity. In all parameters 1,25-dihydroxyvitamin D₃ is about 10 times more active than either 1,24(R)-dihydroxyvitamin D₃ and 1,24(S)-dihydroxyvitamin D₃. In antirachitic activity 1,25-dihydroxyvitamin D₃ is about two times more active than 1α-hydroxyvitamin D₃ which in turn is two times more active than 1,24(R)-dihydroxyvitamin D₃. The 1,24(R)-dihydroxy-vitamin D₃ and 1,24(S)-dihydroxyvitamin D₃ compounds are equally active except in the healing of rickets where the 1,24(S)-dihydroxyvitamin D₃ elicits weak biological activity.