Tetracycline and calcium kinetics are comparable for estimating bone resorption in rats.
(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.
Zhao
Yongdong
Y
Foods and Nutrition Department, Purdue University, West Lafayette, IN 47907, USA.
Cheong
Jennifer M K
JM
Lee
WangHee
W
Wastney
Meryl
M
Martin
Berdine R
BR
Weaver
Connie M
CM
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*
D000900:Anti-Bacterial Agents; D015415:Biomarkers; D013752:Tetracycline; D002118:Calcium