Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: 12/1/2004
Publication Date: 3/4/2005
Citation: Sattler, J.A., Soule, M.R., Hillegonds, D.J., Roughead, Z.K., Wagner, J.L. 2005. Whole body versus skeletal calcium (Ca) retention in rats: Short and long term comparisons using 47CA and 41Ca tracers [abstract]. The Federation of American Societies for Experimental Biology Journal. 19(4):A60.
Technical Abstract: Aim: 1) To determine if whole body Ca retention reflects skeletal uptake of Ca; 2) to evaluate the feasibility of using urinary 41Ca for measurement of bone resorption. Design: Adult, female, Sprague-Dawley rats were injected intra-peritoneally with 0.8 (n=16) or 4 micro Ci (n =56) of 47Ca radiotracer; a subset (n =42) received a 2 nCi dose of 41Ca. To model the short term kinetics of the tracer in the body, its fractional retention in the whole body, heart, plasma, vertebrae (L5), tibia head and midshaft, muscle, as well as its total elimination in the urine and feces were determined, at regular intervals, by gamma-scintillation counting. The data for the first 15 d are reported (mean ± SD). Long term kinetics (41Ca data) will be presented at EB. Results: Fecal excretion was the primary route of elimination of the absorbed Ca and was ~5 times higher than the urinary route. At 48 h, an estimated 92 ± 2 (% dose) was retained in bone and only negligible amounts (<0.02%) were detected in the plasma, heart, and muscle compartments. Based on a single exponential model fit to the retention data, the biological half-life of the tracer was 98 ± 18 d. On d 15, the whole body retention of the tracer was 85 ± 3 (% dose), all of which resided in the bone. During the first 15 d, body Ca retention correlated strongly with skeletal Ca retention (R2 = 0.99, n=49). Conclusion: Whole body Ca retention can be used as an accurate surrogate measure of Ca retention in the skeleton.