strontium-radioisotopes and Osteoporosis--Postmenopausal

The pyridinium cross-links of collagen pyridinoline (Pyd) and deoxypyridinoline (Dpd) are released during bone resorption and are neither metabolized nor absorbed from the diet. The aim of this study was to validate their use in osteoporosis. We studied 19 women with osteoporosis and estimated the bone resorption rate from a combined calcium balance/kinetics technique without (R) and with partial (R(H)) and "complete" (Res) correction for long-term exchange. The strongest correlation was observed between the bone-specific marker (Dpd) and with complete correction for long-term exchange (Res) (r = 0.71, p < 0.001). The intercept was not different from zero, suggesting that bone was the major source for Dpd. The crude ratio of Dpd to Res in the 19 women was 54.5; but the regression coefficient relating Dpd as the dependent variable to Res was 31.8 (95% CI 15.6-48.0), which was higher, but not significantly, than the ratio between Dpd and calcium (16.4) in 10 bone samples (cortical and trabecular bone). The weakest correlations between a biochemical marker and a kinetic index were those between hydroxyproline (a nonspecific marker of bone resorption) and R or R(H). Treatment with hormone replacement therapy (HRT) or HRT and parathyroid hormone peptide 1-38 in seven women over 1 year resulted in similar percent changes in the biochemical markers and estimates of bone resorption. We conclude that the measurement of Dpd provides a reasonably accurate assessment of bone resorption in osteoporosis, and in the context of several repeat 24-h collections of urine offers measurement precision that is similar to that obtainable with methods depending on the use of radioisotopic tracers and the assessment of metabolic calcium balance.

Topics: Aged; Biomarkers; Bone Resorption; Calcium; Chromatography, High Pressure Liquid; Cross-Linking Reagents; Estrogen Replacement Therapy; Female; Humans; Hydroxyproline; Kinetics; Middle Aged; Osteoporosis, Postmenopausal; Parathyroid Hormone; Peptide Fragments; Pyridinium Compounds; Strontium Radioisotopes; Whole-Body Counting

1. Stable strontium (Sr) has been proposed as an alternative to calcium (Ca) isotopes for the measurement of intestinal Ca absorption. The aim of this study was to compare the time course and fractional absorption of Ca and Sr, when both are measured using dual-tracer techniques. 2. 45Ca and Sr absorption tests were carried out on consecutive days in patients with osteoporosis (n = 10) or chronic renal failure (n = 7). Both tests were repeated in four patients with chronic renal failure after treatment with calcitriol (1 microgram daily for 10 days). 3. The time course of Ca absorption was determined using the 85Sr (intravenous)/45Ca (oral) dual-tracer technique, and the time course of Sr absorption using 85Sr (intravenous)/stable Sr (oral). Oral tracers were administered on consecutive days with a test meal containing 5.3 mmol of Ca and 2.5 mmol of either stable Sr or Ca carrier. The fractional absorption of 45Ca and Sr at 6h (FA360) and the absorption rate as a function of time were calculated by deconvolution. 4. The mean FA360 for Sr (20.2%) was lower than the mean FA360 for 45Ca (37.8%, P < 0.001, paired t-test), but the time course of Sr absorption was similar to that of Ca. There was a significant correlation between the FA360 for 45Ca and Sr, although the relationship was improved by including a quadratic term (R2 = 0.89, P < 0.001, significance of quadratic term, P < 0.05). After 1,25-dihydroxyvitamin D treatment, the FA360 of stable Sr increased 4.29-fold, whereas the FA360 of 45Ca increased only 2.4-fold.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adult; Aged; Calcitriol; Calcium; Calcium Radioisotopes; Female; Humans; Intestinal Absorption; Kidney Failure, Chronic; Male; Middle Aged; Osteoporosis, Postmenopausal; Strontium; Strontium Radioisotopes; Time Factors

The authors investigated in three experiments the blood flow (by retention of 85Sr microparticles), the 85Sr retention and state of mineralization of the tibia in female rats after oophorectomy (OOX). In the first experiment one month after OOX the retention of 85Sr microparticles is increased significantly to 158.6%, as compared with controls, the blood flow is increased insignificantly to 131.3%. In the second experiment the retention of microparticles is increased maximally 4 weeks after OOX to 152.9%, the blood flow after two weeks to 150.0%, as compared with controls; the weight of the ash per unit of bone volume of the tibia is significantly reduced after 8 weeks following OOX--to 90.8%. The two-hour retention of radioactive strontium 85Sr in the third experiment after OOX rises--significantly after 8 weeks to 133.4%. The results of the experiments are consistent with the idea on an increased metabolic activity of osseous tissue in the initial stage of the demineralization process following OOX.

Topics: Animals; Bone Density; Female; Humans; Osteoporosis, Postmenopausal; Ovariectomy; Ovary; Radionuclide Imaging; Rats; Regional Blood Flow; Strontium Radioisotopes; Tibia