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Extrarenal metabolism of 25-hydroxycholecalciferol in the rat: regulation by 1,25-dihydroxycholecalciferol. 1984

R T Turner, and R C Avioli, and N H Bell

To determine the role of the kidney in regulation of 25-hydroxycholecalciferol (25OHD3, metabolism, the effects of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] on 3H-25OHD3 were compared in intact and nephrectomized vitamin D-deficient rats. Sixteen hours after the intravenous administration of 3H-25OHD3, extracts of serum and pooled small intestinal mucosa were fractionated by Sephadex LH-20 column chromatography followed by high performance liquid chromatography. In intact rats, 1,25(OH)2D3 (50 ng/day i.p. for 7 days) increased mean serum 3H-24,25-dihydroxycholecalciferol [3H-24,25(OH)2D3] from 2 +/- 2-210 +/- 80 fmol/ml (mean +/- 1 SD), increased mean serum 3H-25,26-dihydroxycholecalciferol [3H-25,26(OH)2D3] from 2 +/- 2-12 +/- 6 fmol/ml and lowered mean serum 3H-1,25(OH)2D3 from 210 +/- 40-4 +/- 4 fmol/ml. Similarly, in nephrectomized animals, 1,25(OH)2D3 increased mean serum 3H-24,25-(OH)2D3 from 6 +/- 11-115 +/- 30 fmol/ml and increased mean serum 3H-25,26(OH)2D3 from 3 +/- 3-26 +/- 10 fmol/ml. Nephrectomy increased serum 3H-25(OH)D3 in untreated (from 1450 +/- 225-2675 +/- 225 fmol/ml serum) and 1,25(OH)2D3 treated rats (from 1600 +/- 175-3075 +/- 100 fmol/ml). 3H-1,25(OH)2D3 averaged 74 +/- 16% of total radioactivity in intestinal mucosa of untreated intact rats and was not detected in either the serum or intestinal mucosa of nephrectomized animals. The results suggest that in intact animals, extrarenal synthesis can account for substantial 24,25(OH)2D3 production and for most 25,26(OH)2D3 production.(ABSTRACT TRUNCATED AT 250 WORDS)

UI MeSH Term Description Entries
D007668 Kidney Body organ that filters blood for the secretion of URINE and that regulates ion concentrations. Kidneys
D009392 Nephrectomy Excision of kidney. Heminephrectomy,Heminephrectomies,Nephrectomies
D002112 Calcifediol The major circulating metabolite of VITAMIN D3. It is produced in the LIVER and is the best indicator of the body's vitamin D stores. It is effective in the treatment of RICKETS and OSTEOMALACIA, both in azotemic and non-azotemic patients. Calcifediol also has mineralizing properties. 25-Hydroxycholecalciferol,25-Hydroxyvitamin D 3,25-Hydroxycholecalciferol Monohydrate,25-Hydroxyvitamin D3,Calcidiol,Calcifediol Anhydrous,Calcifediol, (3 alpha,5Z,7E)-Isomer,Calcifediol, (3 beta,5E,7E)-Isomer,Calderol,Dedrogyl,Hidroferol,25 Hydroxycholecalciferol,25 Hydroxycholecalciferol Monohydrate,25 Hydroxyvitamin D 3,25 Hydroxyvitamin D3,Anhydrous, Calcifediol,Monohydrate, 25-Hydroxycholecalciferol
D002117 Calcitriol The physiologically active form of vitamin D. It is formed primarily in the kidney by enzymatic hydroxylation of 25-hydroxycholecalciferol (CALCIFEDIOL). Its production is stimulated by low blood calcium levels and parathyroid hormone. Calcitriol increases intestinal absorption of calcium and phosphorus, and in concert with parathyroid hormone increases bone resorption. 1 alpha,25-Dihydroxycholecalciferol,1 alpha,25-Dihydroxyvitamin D3,1, 25-(OH)2D3,1,25(OH)2D3,1,25-Dihydroxycholecalciferol,1,25-Dihydroxyvitamin D3,1 alpha, 25-dihydroxy-20-epi-Vitamin D3,1,25(OH)2-20epi-D3,1,25-dihydroxy-20-epi-Vitamin D3,20-epi-1alpha,25-dihydroxycholecaliferol,Bocatriol,Calcijex,Calcitriol KyraMed,Calcitriol-Nefro,Decostriol,MC-1288,MC1288,Osteotriol,Renatriol,Rocaltrol,Silkis,Sitriol,Soltriol,Tirocal,1 alpha,25 Dihydroxyvitamin D3,1,25 Dihydroxycholecalciferol,1,25 Dihydroxyvitamin D3,1,25 dihydroxy 20 epi Vitamin D3,Calcitriol Nefro,D3, 1 alpha,25-Dihydroxyvitamin,D3, 1,25-Dihydroxyvitamin,D3, 1,25-dihydroxy-20-epi-Vitamin,KyraMed, Calcitriol,MC 1288
D006887 Hydroxycholecalciferols Hydroxy analogs of vitamin D 3; (CHOLECALCIFEROL); including CALCIFEDIOL; CALCITRIOL; and 24,25-DIHYDROXYVITAMIN D 3. Hydroxyvitamins D,Hydroxycholecalciferol
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D013045 Species Specificity The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species. Species Specificities,Specificities, Species,Specificity, Species
D013250 Steroid Hydroxylases Cytochrome P-450 monooxygenases (MIXED FUNCTION OXYGENASES) that are important in steroid biosynthesis and metabolism. Steroid Hydroxylase,Steroid Monooxygenases,Hydroxylase, Steroid,Hydroxylases, Steroid,Monooxygenases, Steroid
D014808 Vitamin D Deficiency A nutritional condition produced by a deficiency of VITAMIN D in the diet, insufficient production of vitamin D in the skin, inadequate absorption of vitamin D from the diet, or abnormal conversion of vitamin D to its bioactive metabolites. It is manifested clinically as RICKETS in children and OSTEOMALACIA in adults. (From Cecil Textbook of Medicine, 19th ed, p1406) Deficiency, Vitamin D,Deficiencies, Vitamin D,Vitamin D Deficiencies
D051381 Rats The common name for the genus Rattus. Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus

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