Studies in Calcium Metabolism. The Fate of Intravenously Injected Radiocalcium in Human Beings 123

Abstract

In the course of studies on the effect of phytates on calcium uptake in man (1) it became necessary to determine the extent to which endogenous calcium in the feces might contribute to the calcium balance. Although this point has been studied by several investigators (2-5), there is considerable disagreement on the significance of the fecal route for calcium excretion in man. Thus Malm (6) has observed that different individuals may exhibit pronounced variations in the fecal calcium excretion and has suggested that extended observations be made on each proposed test subject. Since this approach is not practical-in many cases, it seemed desirable to establish the significance of the endogenous calcium output in the feces under our experimental conditions.5The method chosen for investigation was to inject radiocalcium (Ca45) intravenously and to de-termine its concentration in the serum, urine and feces during several days. Such carried out in animals (7-10), but few such data are available for man (11-13). MATERIAL, DESIGN AND METHODSSubjects. Nine adolescent boys, institutionalized for mental inadequacy, but otherwise normal,6 served in the first study (Experiments A and B). In a later experiment (Experiment C), one individual (No. 57) was selected for intensive study. He was a spastic, but neither clinical nor laboratory examinations revealed any abnormalities in his mineral metabolism. The boys ranged in age from 10.9 to 15.7 years, with mean and median ages of 12.6 years. Their height ranged from 124 to 160 cm. with mean and median heights of 142 cm. Their weight ranged from 29.8 to 44.5 kgm., with a mean weight of 35.6 kgm., and a median weight of 36.0 kgm. The mental age of the boys averaged 7.2 years, (median: 7.2 years) and ranged from 5.8 to 9.2 years.The young male adult in Experiment C was 21 years old, weighed 51.4 kgm. and had a mental age of 10.0 years.Design. The subjects (Experiments A and B) were divided into two groups. One group (I.V.) was given the Cae intravenously, while the other group (P.O.) received Cae by mouth. One month later, the P.O. group received the intravenous injection, while the I.V. group received the isotope orally.7 This was done to minimize the effect of periodic or seasonal variations (6,14) and to use each individual as his own control. Preliminary tests had shown that one month after the administration of 0.7 /Ac Cae, the level of Ca' in the blood and in the excreta was no longer measurable. Two years later (Experiment C), one individual was studied intensively 6All of the subjects were under medical care and observation during their usually indefinite institutionalization. They were selected on the basis of clinical examination. Roentgenographs of the chest, knees, hands, skull and spine of six subjects (Nos. 10,11,13,14,15,16) were evaluated by an experienced roentgenologist, who concluded that they did not deviate from the normal range with respect to calcification.7The results on the study with ingested Ca will be presented elsewhere. Methods of analysis for Ca' an...

41Ca and Accelerator Mass Spectrometry to Monitor Calcium Metabolism in End Stage Renal Disease Patients

“…Bronner et al (40 ) showed that 5 days after adolescent boys received 45 Ca intravenously, the total quantity of 45 Ca excreted did not exceed 15% of the dose. These authors contended that nearly all of the calcium that enters the body at a given time is first retained, presumably in the skeleton (40 ). It should be noted that initially after an intravenous dose of labeled calcium, most of the label is found in quiescent surface that is in dynamic equilibrium with blood (41 ).…”

“…Calcium exists naturally as 6 stable isotopes, with the most abundant isotope being 40 Ca. Stable ( 42 Ca, 44 Ca, and 46 Ca) and short-lived radioactive isotopes ( 45 Ca and 47 Ca) of calcium have been used to study calcium metabolism for years (1)(2)(3).…”

“…1, AMS 41 Ca measurements were accomplished via (a) ionization of CaF 2 /silver mixture, (b) selection of 97 or 98 m/z ions (target ions are 40 CaF 3 Ϫ and 41 CaF 3 Ϫ , respectively), (c) acceleration of ions through 9 ϫ 10 6 V, (d) removal of the 3 fluorine atoms and 9 electrons from the calcium atom through charge exchange in a thin carbon foil at the high-voltage terminal to destroy any molecular interferences, (e) a second stage of acceleration to ground potential, (f) measurement of 40 Ca 8ϩ in an offset Faraday cup, and (g) ion identification and single-particle counting of 41 Ca 8ϩ in a multianode gas ionization detector. The details of the AMS analysis can be found elsewhere (4 ).…”

Calcium Metabolism of the Normal Rhesus Monkey*

“…During a short period of acclimatization and observation, the monkeys were maintained on a nutritionally adequate diet 2 triturated with 120 to 200 nmg calcium as the chloride. This labeled meal was offered for 30 minutes and the uneaten residue was analyzed for Ca" and total Ca content.…”

“…The data from studies of the calcium metabolism of 29 normal rhesus monkeys (Macaca mulatta) are being reported in this communication, and compared with the data from similar studies on human beings conducted by this (2,7,8) and by other (3-6, 9-16) laboratories.…”