3H-tetracycline as a proxy for 41Ca for measuring dietary perturbations of bone resorption

Abstract

Our group is interested in evaluating early effects of dietary interventions on bone loss. Postmenopausal women lose bone following reduction in estrogen which leads to increased risk of fracture. Traditional means of monitoring bone loss and effectiveness of treatments include changes in bone density, which takes 6 months to years to observe effects, and changes in biochemical markers of bone turnover, which are highly variable and lack specificity. Prelabeling bone with 41 Ca and measuring urinary 41 Ca excretion with accelerator mass spectrometry provides a sensitive, specific, and rapid approach to evaluating effectiveness of treatment. To better understand 41 Ca technology as a tool for measuring effective treatments on reducing bone resorption, we perturbed bone resorption by manipulating dietary calcium in rats. We used 3 H-tetracycline ( 3 H-TC) as a proxy for 41 Ca and found that a single dose is feasible to study bone resorption. Suppression of bone resorption, as measured by urinary 3 H-TC, by dietary calcium was observed in rats stabilized after ovariectomy, but not in recently ovariectomized rats.

Doxycycline reduces osteopenia in female rats

“…It is well known that doxycycline chelates divalent metals 66 and this interaction between doxycycline and divalent metal calcium is important for the health of bone tissue, as in the study of Weaver and colleagues sought to measure bone quality via the urinary excretion of Calcium isotopes. The authors used an isotope of tetracycline to make this measurement and with that, the authors could measure almost immediately the differences after induction of osteopenia by ovariectomy 79 .…”

Biochemical paths in humans and cells: Frontiers of AMS bioanalysis

“…Certain isotopes, such as 26 Al and 41 Ca became usefully available in biomedical research only through AMS quantification, and both isotopes continue to be used in biological research [12,13], and 41 Ca is poised (as it long has been) to become an important clinical tool in quantifying bone turnover due to disease [14]. We present here an update on organic biomedical AMS after 17 years experience, with particular attention to areas that seem particularly suited to the specificity and sensitivity of AMS, such as molecular assays, biochemical tracing in humans, regeneration periods of human tissues, and the potential for quantifying metabolite concentrations within single cells.…”