Liquid scintillation based quantitative measurement of dual radioisotopes (3H and 45Ca) in biological samples for bone remodeling studies

Acute and prolonged bone complications associated with radiation and chemotherapy in cancer survivors underscore the importance of establishing a laboratory-based complementary dual-isotope tool to evaluate short- as well as long-term bone remodeling in an in vivo model. To address this need, a liquid scintillation dual-label method was investigated using different scintillation cocktails for quantitative measurement of 3H-tetracycline (3H-TC) and 45Ca as markers of bone turnover in mice. Individual samples were prepared over a wide range of known 45Ca/3H activity ratios. Results showed that 45Ca/3H activity ratios determined experimentally by the dual-label method were comparable to the known activity ratios (percentage difference ∼2%), but large variations were found in samples with 45Ca/3H activity ratios in range of 2–10 (percentage difference ∼20–30%). Urine and fecal samples from mice administered with both 3H-TC and 45Ca were analyzed with the dual-label method. Positive correlations between 3H and 45Ca in urine (R=0.93) and feces (R=0.83) indicate that 3H-TC and 45Ca can be interchangeably used to monitor longitudinal in vivo skeletal remodeling.

► Liquid scintillation cocktails support accurate dual-label analysis of 3H and 45Ca.
► 3H-tetracycline and 45Ca were highly correlated in mice urine and feces.
► 3H-tetracylcine and 45Ca can be used to monitor in vivo temporal bone remodeling.