Direct Measurement of Osteolysis in Man

Abstract

A B S T R A C T Precise, direct measurement of bone calcium release (vo) has been accomplished using a continuous tracer administration (CTA) technique. Dietary calcium (96.97% 4OCa) is replaced by 4OCa (99.991% 40Ca) and blood levels of the naturally occuring isotope 48Ca are monitored by neutron activation analysis as a function of time. 48Ca abundance falls as this isotope is excreted and only partially replaced by release from bone. After a suitable period, an asymptotic abundance of 48Ca in serum, E, is approached which is the fraction of the turnover rate of the rapidly exchangeable calcium pools coming from the skeleton (E = V/Vt). E is determined with a standard error of 2%, providing a precise, sensitive index of v,. 13 studies in three normal men and one postmenopausal woman receiving maintenance estrogen show large intersubject variations in parameters of calcium metabolism using both CTA and pulse tracer administration (PTA) plus balance techniques. Induced hypercalcemia results in a prolonged decrease in vo. Glucocorticoid therapy initially and consistently induces a marked hypercalciuria while effects on most other parameters of calcium kinetics are variable. In two men E fell when testosterone was added to glucocorticoid treatment, consistent with the known antiosteolytic effect of androgens, despite the short period of study.

Effects of ethane-1-hydroxy-1,1-diphosphonate (EHDP) upon the kinetics of bone resorption and bone formation at the whole bone level in prelabelled chicks

“…Using the blood-bone ratio of 45Ca as an index of bone resorption in prelabelled animals, it has been shown [31] that chicks are different from rats in that chicks normally maintain their basal bone resorption constant during active growth, which is similar to that observed in man [32], while rats decrease their basal bone resorption [25,31]. When the rate of 3H-tetracycline loss from bone is measured, the basal rate of bone resorption in the rapidly growing chicks [25] is four times faster than that observed in rapidly growing rats [31,33].…”

Low Bone Mineral Density in Anorexia Nervosa: Treatments and Challenges

“…Hypercortisolemia-Elevated cortisol levels may also be an important mediator of low bone mass in anorexia nervosa. The negative effects of cortisol on bone are the result of a number of mechanisms including decreased calcium availability via a decrease in calcium absorption in the intestine and an increase in urinary calcium excretion [102][103][104], an impairment of bone formation via reduced osteoblast proliferation [105], and an increase in bone resorption due in part to inhibition of gonadotropin secretion [106]. Levels of cortisol are higher in individuals with anorexia nervosa, a physiologically stressful state, as compared to normal-weight controls [107][108][109][110] and cortisol is inversely correlated with bone formation markers and BMD in adolescent girls and in women with anorexia nervosa [25,109,110].…”

Inductively Coupled Plasma Mass Spectrometric Analysis of Calcium Isotopes in Human Serum: A Low-Sample-Volume Acid-Equilibration Method

“…This is because virtually all of these studies have used analytical approaches in which 500 L or more of serum was required for the oxalate precipitation or ion-exchange methods used to prepare the samples for analysis. Most analyses have involved thermal ionization mass spectrometry (TIMS), 3 using either quadrupole or magnetic sectorbased spectrometers (1,2 ).…”

“…Stable calcium isotope tracers have been used extensively for ϳ30 years for metabolic studies of calcium homeostasis in humans in a variety of clinical areas (1)(2)(3)(4)(5)(6)(7). Stable isotopes are safe for use in humans of all ages and do not have problems related to the disposal of contaminated waste, a major advantage over radioisotopes.…”