Metabolism of 1alpha-hydroxyvitamin D3 in the chick.
Chicks convert both orally and intravenously administered 1alpha-hydroxy[6-3H]vitamin D3 rapidly to 1alpha,25-dihydroxy[6-3H]vitamin D3. The maximal accumulation of 1alpha,25-dihydroxy[6-3H]vitamin D3 in intestine precedes the intestinal absorption response to 1alpha-hydroxyvitamin D3 by at least 2 hours. Oral administration results in the highest concentrations of 1alpha,25-dihydroxy[6-3H]vitamin D3 in intestine, giving a level about 1.5 times that achieved with an intravenous dose. On the other hand, an oral dose of 1alpha-hydroxy[6-3H]vitaminD3 gives much lower amounts of both 1alpha-hydroxy[6-3H]vitamin D3 and 1alpha,25-dihydroxy[6-3H]vitamin D3 in bone and blood than an intravenous dose, which suggests that the 1alpha-hydroxy[6-3H]vitamin D3 may not be utilized as well by the oral route as by an intravenous route. Liver homogenates from both rat and chick convert 1alpha-hydroxy[6-3H]vitamin D3 to 1alpha,25-dihydroxy[6-3H]vitamin D3. However, intestinal homogenates from chick, but not rat, can also cary out this conversion, which may account for the higher concentration of 1alpha,25-dihydroxy[6-3H]vitamin D3 found in the intestine of chicks given an oral dose of 1alpha-hydroxy[6-3H]vitamin D3.
D000818:Animals; D001693:Biological Transport, Active; D001842:Bone and Bones / Q000378:metabolism; D002645:Chickens; D004100:Dihydroxycholecalciferols / Q000096:biosynthesis; D006887:Hydroxycholecalciferols / Q000378:metabolism*; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007421:Intestine, Small / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D009928:Organ Specificity; D051381:Rats; D013045:Species Specificity; D014808:Vitamin D Deficiency / Q000378:metabolism
D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols