1. Metabolism and biologica.
- Author
-
Holick MF, Baxter LA, Schraufrogel PK, Tavela TE, and DeLuca HF
- Subjects
- Animals, Bile metabolism, Biological Assay, Bone and Bones metabolism, Calcium metabolism, Dihydroxycholecalciferols blood, Dihydroxycholecalciferols pharmacology, Intestinal Absorption drug effects, Intestine, Small metabolism, Liver metabolism, Male, Organ Specificity, Rats, Species Specificity, Structure-Activity Relationship, Chickens metabolism, Dihydroxycholecalciferols metabolism, Hydroxycholecalciferols metabolism
- Abstract
24R,24,25-Dihydroxyvitamin D3 is capable of inducing a minimal intestinal calcium transport response in chicks when compared to an equal amount of 25-hydroxyvitamin D3. 1,24,25-Trihydroxyvitamin D3 is also less active than 1,25-dihydroxyvitamin D3, and its activity is much shorter lived than that of 1,25-dihydroxyvitamin D3. A comparison of the metabolism of 25-hydroxy[26,27-3H]vitamin D3 and 24,25-dihydroxy[26,27-3H]vitamin D3 in the rat and chick shows that 24,25-dihydroxyvitamin D3 and 1,24,25-trihydroxyvitamin D3 disappear at least 10 times more rapidly from the blood and intestine of chicks. Furthermore, examination of the excretory products from both of these species demonstrates that chicks receiving a single dose of 24,25-dihydroxy[26,27-3H]vitamin D3 excrete 66% of the total radioactivity by 48 hours, whereas rats receiving the same dose excrete less than one-half that amount. These results demonstrate that 24,25-dihydroxyvitamin D3 is considerably less biologically active in the chick than in the rat, probably due to more rapid metabolism and excretion.
- Published
- 1976