Effect of dietary mineral and vitamin D content and parathyroidectomy on the plasma disappearance rate of 1,25-dihydroxyvitamin D3 in rats.
The plasma disappearance rate of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] was determined in rats after a single intravenous injection of the tritiated hormone. Tritiated 1,25-(OH)2D3 (120 Ci mmol-1) was administered to rats at a dose of 400 000 dpm kg-1 body weight and the animals were bled between 0 and 8 hours. The dose was estimated to produce negligible perturbations in endogenous plasma levels of 1,25-(OH)2D3. The plasma disappearance of 3H-1,25-(OH)2D3 occurred in two phases. The second phase plasma half-life of 1,25-(OH)2D3 in immature 25- to 35-day-old animals (4.7 hours) was significantly shorter than the second phase plasma half-life of maturing 49- to 65-day-old animals (8.0 hours). Phosphorus deprivation for 12 days significantly prolonged the second phase plasma half-life of 1,25-(OH)2D3 from a control value of 4.9 hours to 10.4 hours. Parathyroidectomy, regardless of the plasma calcium concentrations, shortened the second phase plasma half-life of 1,25-(OH)2D3 from control values of 9.1 hours to 5.0 hours. Calcium deprivation for 7 days did not alter the second phase plasma half-life of 1,25-(OH)2D3. Vitamin D deprivation for 5 weeks increased the second phase plasma half-life from 11.0 to 19.9 hours but the difference was not significant.
D000367:Age Factors; D000818:Animals; D002117:Calcitriol / Q000097:blood*; D002118:Calcium / Q000097:blood; D002136:Calcium, Dietary / Q000494:pharmacology*; D004032:Diet; D005260:Female; D006207:Half-Life; D008297:Male; D010280:Parathyroid Glands / Q000502:physiology* / Q000601:surgery; D010758:Phosphorus / Q000172:deficiency / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D014807:Vitamin D / Q000494:pharmacology*; D014808:Vitamin D Deficiency / Q000097:blood
D002136:Calcium, Dietary; D014807:Vitamin D; D010758:Phosphorus; D002117:Calcitriol; D002118:Calcium