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  • Title: Importance of the stereochemical position of the 24-hydroxyl to biological activity of 24-hydroxyvitamin D3.
    Author: Tanaka Y, Frank H, DeLuca HF, Koizumi N, Ikekawa N.
    Journal: Biochemistry; 1975 Jul 29; 14(15):3293-6. PubMed ID: 1148204.
    Abstract:
    Both stereoisomers of 24-hydroxyvitamin D3, i.e. 24(S)-hydroxyvitamin D3 and 24(R)-hydroxyvitamin D3, stimulate intestinal calcium transport almost equally well in the rat. The duration of effect is somewhat shorter for the 24(S)-hydroxyvitamin D3 than for the 24(R)-hydroxyvitamin D3. However, the 24(S)-hydroxyvitamin D3 has little or no activity in the mobilization of calcium from bone, in the growth of rats on a low calcium diet, in the elevation of serum phosphorus of rachitic rats, or in the calcification of bone. On the other hand, the 24(R)-hydroxyvitamin D3 is almost as active as 25-hydroxyvitamin D3 in all of these systems, although its activity is not always of equal duration to that of 25-hydroxyvitamin D3. The selectivity of these systems for only one of the 24-hydroxy stereoisomers supports the idea that in vivo 24-hydroxylation of vitamin D compounds is of functional importance.
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