Joseph Samachson

The reaction of 65Zn with the surfaces of bone and bone mineral

Abstract 1. 1. The uptake of 47 Ca and 65 Zn by bone powder and by inorganic bone was determined in the presence of various carriers. The uptake of 65 Zn by bone powder shaken for 2 h at pH 6 with solutions of the radioisotopes, whether without added carrier or in the presence of 2.5 mM of stable calcium, was about 90%, greatly exceeding the uptake of 47 Ca. The addition of 2.5 mM of zinc carrier, however, decreased the uptake of both 65 Zn and 47 Ca. 2. 2. The uptake of 65 Zn by inorganic bone was even greater than that by bone powder, approaching 100% in 5 min, and made it clear that the mineral part of bone showed a great preference for 65 Zn. 3. 3. Experiments on radioisotope uptake at pH 7.0, in the presence of creatinine to prevent precipitation of the zinc, gave results similar to those obtained at pH 6. 4. 4. The uptake of 65 Zn by bone was reduced by ethylenediaminetetraacetic acid, a strong chelating agent, to about 0.3% at pH values from 5 to 9, while the uptake of 65 Zn by inorganic bone was reduced under the same conditions to about 1%. 5. 5. The effect of natural chelating agents in binding serum zinc explains why zinc does not occur in even higher concentrations than are actually found in bones and teeth.

Fluoride analysis of the human diet and of biological samples

Abstract Fluoride analysis of the human diet and of excreta were determined using certain modifications of the diffusion method of Singer and Armstrong. This study deals specifically with the fluoride analysis of the diet and stool, although numerous analyses of urine, saliva, and plasma were also carried out. The dietary fluoride content averaged 1.51 ± 0.11 mg per day in the early studies and 1.81 ± 0.08 mg in later studies. The fecal and urinary fluoride content depended on the dietary fluoride intake. The details of the method of analysis of the diet and of the biological samples are described.

INHIBITION OF RADIOSTRONTIUM ABSORPTION BY ALUMINUM PHOSPHATE GEL IN MAN AND ITS COMPARATIVE EFFECT ON RADIOCALCIUM ABSORPTION.

Abstract Studies performed under constant and strictly controlled dietary conditions have shown that a single oral dose of aluminum phosphate gel, ranging from 300 ml to 100 ml, given immediately prior to the oral dose of 85Sr decreased the absorption of 85Sr in man by an average of 87·5 per cent. An amount of 100 ml aluminum phosphate gel was as effective as 300 ml in decreasing the absorption of 85Sr. The decrease in 47Ca absorption was considerably less than the decrease in 85Sr absorption, averaging 37·8 per cent. The disproportionate decrease in 47Ca and 85Sr absorption in the aluminum phosphate gel studies resulted in a marked increase in the 47Ca/85Sr discrimination ratio of the absorption and of the plasma levels of these radio-isotopes. A comparison of the absorption of 47Ca and 85Sr determined in the same patients in the aluminum phosphate gel studies showed an average 47Ca/85Sr discrimination ratio of 12·9 as compared to a value of 1·62 in the control studies. The aluminum phosphate gel studies have shown that this non-toxic, well-tolerated substance is effective in inhibiting the absorption of acutely ingested radiostrontium in man and that this compound decreases the absorption of 47Ca to a considerably lesser extent.

INHIBITION OF RADIOSTRONTIUM ABSORPTION IN MAN.

Abstract The ingestion of aluminum phosphate gel with breakfast caused an average 87 per cent decrease of the intestinal absorption of radiostrontium in man as judged by two different criteria: the marked decrease in the Sr85 plasma levels and the increase in the fecal Sr85 excretions after administration of an oral tracer dose.

Atomic-Absorption Spectrophotometry in Mineral and Trace-Element Studies in Man

Analyses of calcium, magnesium, and zinc in the diet and in urine and stool have been performed with the atomic-absorption spectrophotometer. Complete metabolic balance studies of calcium, magnesium, and zinc were performed under constant metabolic conditions in man during different intake levels of these elements. These studies have led to a better understanding of the interrelationship of minerals and trace elements in man.

The reactions of H+ and Zn2+ with the surfaces of bone and bone mineral

1. n1. Although the greater uptake by bone and bone mineral of 65Zn2+ than of 47Ca2+ as previously reported1 was confirmed, it was also found that the fraction of bone Ca2+ exchanged, due to the differences between isoionic and heteroionic exchange, was in some cases the same for the two radioisotopes. n n2. n2. 65Zn2+ was taken up by bone and bone mineral much more rapidly than 47Ca2+ in the initial stages of reaction. However, as uptake continued, diffusion through bone appeared to become the rate-limiting process. Apparently this differed little for the two radioisotopes. n n3. n3. The amount of Ca2+ that entered the solution in these exchange experiments was equal to the amount of Zn2+ that entered bone powder at pH 7.3 and anorganic bone at pH 6.0. Ca2+ in solution was greater than Zn2+ entering bone powder at pH 6.0, and less than Zn2+ entering anorganic bone at pH 7.3. n n4. n4. H+ was shown to be a powerful competitor of Ca2+ in exchange reactions, with a superiority of about 1000: 1. A mechanism was proposed to explain its behavior. n n5. n5. Zn2+ replaced Ca2+ on the surface of bone mineral so rapidly that it protected the surface from attack by H+ at pH 6.0. It thus blocked the mechanism of action of H+, suppressed much of the rise in pH that was found in its absence, and reduced to a considerable extent the amount of phosphate that entered the solution. These effects were interesting from the theoretical point of view, and are of potential practice importance. n n6. n6. After bone powder or anorganic bone was shaken with solutions containing Zn2+, stable Mg2+ was found in the solutions in amounts up to 0.23 mmole/l. In some cases it was as much as 20% of the Zn2+ that entered bone by heteroionic exchange. n n7. n7. Ca2+/P ratios of solutions which had been shaken with bone and bone mineral were either significantly greater than or significantly less than the ratios in the original bone samples and in theoretical hydroxyapatite, depending on conditions. These, and other data, suggest that the increase in Ca2+ and P concentration in solution had little to do with solubility proper but was the result of chemical reaction. n n8. n8. Bone powder and anorganic bone differed in quantitative aspects of their relations with 47Ca2+, 65Zn2+, H+, and stable Ca2+ and P. Differences with regard to pH and rate of dissolution of bone mineral in the two forms were especially striking, and suggested that anorganic bone, as usually prepared, differed from bone powder not only in its lack of organic matrix, but in relative content of amorphous phosphate and crystalline hydroxyapatite as well.

EFFECT OF HIGH PHOSPHORUS INTAKE ON SR85 EXCRETIONS IN MAN.

Summary The effect of high phosphorus intake on radiostrontium absorption was investigated in 6 patients. Two of these were studied during low calcium diet, 2 during high calcium intake, and 2 patients during low and high calcium intake. Addition of phosphorus to the diet led to a decrease in Sr85 absorption in 3 of the 4 patients each studied during low and high calcium intake, respectively. Urinary Sr85 excretion and urinary calcium excretion were decreased during high phosphorus intake in both the low and high calcium studies. The authors wish to thank Mrs. Vernice Vankin-scott, Head Nurse, Metabolic Research Unit, for most valuable assistance in this study.

Effect of Ethylenediaminetetraacetic Acid on Radiostrontium Excretion in Man.

Summary The effect of sodium salt of ethylenediaminetetraacetic acid, Na-EDTA, upon radiostrontium (Sr85) metabolism in man was investigated under controlled metabolic conditions. Urinary radiostrontium excretion was inhibited in each of 3 patients when Na-EDTA was infused. This depression was followed by excess excretion of the isotope after discontinuation of Na-EDTA. The mechanism of action responsible for this metabolic shift is discussed.

Effect of Metal Ions on the Relative Uptake of Ca45 and Sr85 by Bone Powder in Vitro

ABS>The ratio of uptake of Ca/sup 45/ to that of Sr/sup 85/ by defatted bone powder in vitro was used as a parameter for the study of bone surfaces. To test the hypothesis that one difference between sites where ions exchange was the space available on the crystal surface, defatted bone powder was treated with metallic ions of different radii and then shaken with solutions containing Sr/sup 85/ and Ca/sup 45/. Alternatively, the metal ions were added to the same solution as the radioisotopes. Uptake was determined both with defatted bone powder and with anorganic bone. The ratio of Ca/sup 45/Sr/sup 85/ uptake was decreased by Be/sup 2+/, Cu/sup 2+/, Co/sup 2+/, Ni/sup 2+/, Mn/sup 2+/, Cd/sup 2+/, Zn/sup 2+/, and Pb/s up 2+/, unaffected by Mg2+, and increased by Ba/sup 2+/. Other factors also influenced the ratio, but, in general, the hypothesis suggested above appeared valid. Reproducibility of individual uptake values, but not of the ratio, was increased by more vigorous shaking. (auth)

Effect of low and high calcium intake on Sr90 metabolism in adult man

Balances of Sr90 have been determined in man under constant dietary conditions during low and high calcium intake but during a similar intake of Sr90. Ten patients were studied during low calcium intake (average 213 mg Ca/day) and 10 patients during high calcium intake (average 1718 mg Ca/day), the latter being attained by adding calcium gluconate tablets to the constant low calcium diet. The average Sr90 intake was similar during low and high calcium intake, 4.6 pCi/day and 5.7 pCi/day, respectively. The average Sr90 balance was slightly more negative during high calcium intake, −0.36 pCi/day, than during low calcium intake, −0.01 pCi/day, however this difference was not significant. Also, there was no significant difference between the percent net absorption of Sr90 during the intake of the low and high calcium diet, 12.3 % versus 6.5% of the Sr90 intake, respectively. The Sr90/Ca ratios of the diet, urine and stool were determined and the Observed Ratios (O.R.) were calculated. The Sr90/Ca ratios of stool/diet were less variable than the Sr90/Ca ratios of urine/diet during the intake of different levels of calcium. Since the Sr90/Ca ratio of stool was similar to the Sr90/Ca ratio of the diet during both low and high calcium intake, the fecal Sr90/Ca ratio can be used for the estimation of the dietary Sr90 intake.