title: Elevated 1,25-dihydroxyvitamin D3 and intestinal calbindin-D9k in the toothless rat.
abstract: The toothless (tl) rat is a nonlethal osteopetrotic mutation characterized by systemic skeletal sclerosis, growth plate morphology suggestive of rickets, and morphological evidence of reduced osteoclastic bone resorption. Vitamin D metabolites, serum calcium and phosphorus levels, and the developmental appearance of vitamin D-dependent intestinal calcium binding protein (calbindin-D9k) was studied in normal and mutant rats of tl stock from 7 to 35 days of age. 1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] was found to be significantly elevated in mutant animals by 7 days of age (71 +/- 9 pM, tl/tl vs. 24 +/- 8 pM, +/?) and continued to increase to a peak of 428 pM at the time of weaning. This was 240% higher than normals at this period. The elevated levels of 1,25-(OH)2D3 stimulated a significant and precocious appearance of intestinal calbindin-D9k in mutants, beginning by 14 days of age and reaching their peak levels at 21 days postpartum (25.6 +/- 1.7 micrograms/mg protein, tl/tl vs. 16.4 +/- 1.5 micrograms/mg protein, +/?). The cause of the elevated circulating levels of 1,25-(OH)2D3 in tl rats is unknown but may be due to the low serum phosphorus levels present in these animals.
authors.affiliation: Department of Anatomy, University of South Dakota School of Medicine, Vermillion 57069.
authors.forename: M F
authors.initials: MF
authors.lastname: Seifert
authors.forename: R W
authors.initials: RW
authors.lastname: Gray
authors.forename: M E
authors.initials: ME
authors.lastname: Bruns
mesh_terms: D000375:Aging; D000818:Animals; D001835:Body Weight; D064026:Calbindins; D002112:Calcifediol / Q000097:blood; D002117:Calcitriol / Q000097:blood / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D004386:Duodenum / Q000254:growth & development* / Q000378:metabolism; D024510:Muscle Development; D009130:Muscle, Smooth / Q000254:growth & development / Q000378:metabolism; D010758:Phosphorus / Q000097:blood; D051381:Rats; D011922:Rats, Mutant Strains; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D014071:Tooth Abnormalities / Q000235:genetics / Q000378:metabolism*
chemical_list: D064026:Calbindins; D064030:S100 Calcium Binding Protein G; C576508:S100g protein, rat; D010758:Phosphorus; D002117:Calcitriol; D002112:Calcifediol; D002118:Calcium