title: Tetracycline and calcium kinetics are comparable for estimating bone resorption in rats.
abstract: (3)H-tetracycline ((3)H-TC) is thought to be superior to calcium (Ca) isotopic tracers for estimating bone resorption rates due to the less redeposition upon release in animal models. However, these 2 tracers have not been compared directly using complete kinetic studies with sampling of blood, urine, feces, and bone. Our goal was to compare the 2 isotopes for evaluating bone turnover. We firstly developed a model for (3)H-TC kinetics in 4-mo-old female rats (n = 3) by measuring the tracer in serum, urine, and feces over 4 d. Then, 9-mo-old ovariectomized (OVX) rats (n = 6) were given both (45)Ca and (3)H-TC subcutaneously. Urine was collected in 24-h pools and assayed for both tracers. Rats were killed 7 and 46 d after the dose and whole skeleton was harvested. We calculated bone resorption rates by modeling the (45)Ca and (3)H-TC data in urine and bone. (3)H-TC kinetics revealed that, like Ca, there are 2 exchangeable compartments between serum and bone. An additional pool was required to account for bone mass of Ca. Bone resorption rates determined from urinary (45)Ca and (3)H-TC did not differ significantly. The tracers (45)Ca and (3)H-TC can be used interchangeably to determine bone resorption rates in OVX rats. Thus, both labels can be used to screen dietary and other interventions for beneficial effects on bone.
authors.affiliation: Foods and Nutrition Department, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Yongdong
authors.initials: Y
authors.lastname: Zhao
authors.forename: Jennifer M K
authors.initials: JM
authors.lastname: Cheong
authors.forename: WangHee
authors.initials: W
authors.lastname: Lee
authors.forename: Meryl
authors.initials: M
authors.lastname: Wastney
authors.forename: Berdine R
authors.initials: BR
authors.lastname: Martin
authors.forename: Connie M
authors.initials: CM
authors.lastname: Weaver
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics; D015415:Biomarkers; D015519:Bone Density; D001862:Bone Resorption / Q000378:metabolism*; D002118:Calcium / Q000493:pharmacokinetics*; D005260:Female; D010052:Ovariectomy; D051381:Rats; D013752:Tetracycline / Q000493:pharmacokinetics*
chemical_list: D000900:Anti-Bacterial Agents; D015415:Biomarkers; D013752:Tetracycline; D002118:Calcium