title: Effects of clodronate on cortical and trabecular bone in ovariectomized rats on a low calcium diet.
abstract: The aim of this study was to evaluate the contribution of a low calcium diet to the cortical and trabecular osteoporosis seen in ovariectomized rats after 7 weeks on a low calcium diet and to investigate the effects of the bisphosphonate clodronate on this development of osteoporosis. Thirty-six mature, female Wistar rats were randomized into four groups: Ovx-B (bisphosphonate) and Ovx-C (control) were ovariectomized, and Sham-Ca (low calcium) and Sham+Ca (normal calcium) were sham operated. The first three groups were fed a low calcium diet (0.01%) and Sham+Ca normal rat chow (Ca 1.1%). The Ovx-B received 10 mg/kg s.c. clodronate daily for nine weeks, and Ovx-C, Sham-Ca, and Sham+Ca received the same volumes of saline. Bone mineral turnover measured as 85Sr-uptake was increased in all low calcium groups compared to Sham+Ca. The Sham+Ca femora had higher dry weight and ash weight than the other groups, and Ovx-C had higher dry weight compared with Ovx-B and Sham-Ca. Calcium content was lower in both Ovx groups compared to both Sham groups. Magnesium was lower in all groups compared to Sham+Ca and higher in Ovx-B compared with Ovx-C. In the femoral shaft, Sham+Ca had significantly higher ultimate bending moment, energy absorption, and deflection compared to the other three groups. Ultimate bending moment was higher in Sham-Ca than in Ovx-C. Stiffness was increased in both Sham+Ca and Ovx-B compared to Ovx-C. The maximum stress in the femoral midshaft was higher in Sham+Ca than in the other groups, and higher in Ovx-B than in Ovx-C. Histomorphometry showed increased medullary area in all low calcium groups compared to Sham+Ca and larger cortical area in Sham+Ca and Ovx-B compared to Ovx-C. Compared to Sham+Ca the trabecular bone volume was decreased to 30% in Sham-Ca and to 9% in Ovx-C, but was unchanged in Ovx-B. The low calcium diet generally increased bone mineral turnover and reduced the tibial bone volume. Femoral changes led to a reduction of cortical fracture strength and maximal stress. Ovariectomy in addition to a low calcium diet reduced femoral strength even more. Daily injections of clodronate to ovariectomized rats on a low calcium diet increased femoral shaft stiffness and maximum stress, and clodronate preserved both trabecular and cortical tibial bone volume completely.
authors.affiliation: Institute for Surgical Research, Rikshospitalet The National Hospital, N-0027 Oslo, Norway.
authors.forename: T S
authors.initials: TS
authors.lastname: Kaastad
authors.forename: O
authors.initials: O
authors.lastname: Reikerâs
authors.forename: J E
authors.initials: JE
authors.lastname: Madsen
authors.forename: S
authors.initials: S
authors.lastname: Narum
authors.forename: J H
authors.initials: JH
authors.lastname: Stromme
authors.forename: K J
authors.initials: KJ
authors.lastname: Obrant
authors.forename: L
authors.initials: L
authors.lastname: Nordsletten
mesh_terms: D000818:Animals; D002136:Calcium, Dietary / Q000008:administration & dosage*; D004002:Clodronic Acid / Q000494:pharmacology*; D004195:Disease Models, Animal; D005260:Female; D005269:Femur; D010024:Osteoporosis / Q000188:drug therapy*; D010052:Ovariectomy; D051381:Rats; D017208:Rats, Wistar; D013326:Strontium Radioisotopes / Q000378:metabolism; D013977:Tibia
chemical_list: D002136:Calcium, Dietary; D013326:Strontium Radioisotopes; D004002:Clodronic Acid