title: Bone resorption and serum levels of vitamin D metabolites in the hypophosphataemic rat.
abstract: The supplementation of a low phosphate diet with vitamin D has been shown to result in an increase in bone resorption in the hypophosphataemic rat. The aim of the present study was to determine if administration of vitamin D to rats fed a vitamin D- and phosphate-depleted diet would result in an increase in the circulatory levels of the active vitamin D metabolite 1,25(OH)2D3 and an associated increase in bone resorption. Three groups of weanling Sprague-Dawley rats were used. The first group consisted of control animals on a normal laboratory stock diet and the second and third groups were experimental animals receiving a vitamin D- and phosphate-deficient diet with the third group receiving vitamin D supplementation. All animals were housed in the dark. After 30 days on the diet the experimental animals received 0.1 mmol NaH2PO4 by intraperitoneal injection. Blood was sampled at zero, 3, 6, 18 and 48 h post-injection and analysed for the vitamin D metabolites 25(OH)D3 and 1,25(OH)2D3, calcium and inorganic phosphate (Pi). The serum analyses revealed that the level of 25(OH)D3 in the hypophosphataemic animals was significantly lower than that of the control animals. However, the 1,25(OH)3D3 level was initially significantly higher, then dropped to the control level at 18 h post-intraperitoneal injection of phosphate. Further, the serum levels of 25(OH)D3 and 1,25(OH)2D3, calcium and Pi in the hypophosphataemic animals supplemented with vitamin D were significantly higher than those of the vitamin D-deficient animals. Also the vitamin D-supplemented animals exhibited significantly greater levels of bone resorption. These results therefore, are consistent with a role of 1,25(OH)2D3 in bone resorption in hypophosphataemic rats.
authors.affiliation: School of Dental Science, University of Melbourne.
authors.forename: A
authors.initials: A
authors.lastname: Malcolm
authors.forename: E
authors.initials: E
authors.lastname: Reynolds
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001824:Body Constitution; D001862:Bone Resorption / Q000209:etiology* / Q000473:pathology; D002112:Calcifediol / Q000097:blood; D002117:Calcitriol / Q000097:blood; D002118:Calcium / Q000097:blood; D017674:Hypophosphatemia / Q000097:blood / Q000150:complications*; D007274:Injections, Intraperitoneal; D010710:Phosphates / Q000008:administration & dosage / Q000097:blood / Q000172:deficiency; D051381:Rats; D017207:Rats, Sprague-Dawley; D014807:Vitamin D / Q000008:administration & dosage / Q000097:blood* / Q000378:metabolism; D014808:Vitamin D Deficiency / Q000150:complications
chemical_list: D010710:Phosphates; D014807:Vitamin D; D002117:Calcitriol; D002112:Calcifediol; D002118:Calcium