RADIOISOTOPES IN THE STUDY OF BONE
ABS>The use of two groups of radioisotopes in bone research is discussed: the alkaline earth elements, such as Ra and Sr, which are taken up like Ca in centers of growing bone; and rare earth elements, such as Y and Pu, which are stored in bone. The physiologic factors underlying uptake of this second group are not understood, and their uptake is much less affected by age than is that of the alkaline earths. P/sup 32/ has also been employed in studies of phosphate binding to collagen in bone. The sequence of events in calcification is best observed by the use of Ca/sup 45/. Administration of Ca/ sup 45/ in the living animal is followed by its deposition in osteons, newly formed as a part of the internal remodeling of compact bone. Here there is discrete radioactivity, demonstrable by autoradiography within minutes after parenteral administration of the isotope, and quickly assuming the appearance of hotspots. In addition to Ca/sup 45/ as an indicator of the mineralization of bone, Ca/sup 47/ and Sr/sup 85/, both gamma emitters, are widely used and have the advantage of applicability to external counting. They are thus suitable for recording gross, over-all distribution in the skeleton and may be used in man as well as in experimental animals, since they do not require biopsy or sacrifice of the subject. Phosphous-32, which is deposited in the bone mineral as phosphate, was the first radioisotope to be applied to the study of bone, but now it has been largely replaced by the isotopes of Ca and Sr. Carbon-14 has been used to demonstrate the deposition of carbonate in the bone mineral, but results so far have been limited mainly to estimation of the biologic half-life of this element in bone. More fruitful has been the use of Na/sup 22/ or Na/sup 24/, since 46% of the total body Na is present in the mineral substance of bone. In observations made 4 to 6 weeks after injection of Na/sup 22/, there was concentration of the radioisotope in osteons in which bone mineral was being deposited at the time of injection; this is evidence for deposition of new Na during initial mineralization. After immersion in a solution of Na/sup 22/Cl, compact bone was found to be uniformly labeled. From a study of the turnover of Mg/sup 28/ in man, it was concluded that there is a relatively large pool with a slow turnover rate, presumably made up largely of the Mg of bone. When Zn/sup 65/ is injected, it is initially deposited in soft tissues, but a large proportion is transferred to the skeleton, where it is held for long periods of time. Zn/ sup 65/ emits BETA and gamma rays and has a halflife of 245 days; it thus presents a potential biologic hazard. Zn/sup 65/ in young monkeys was found from autoradiograms made after 5 days to be exclusively located at the line where preosseous tissue is becoming mineralized. Because of its BETA radiation, Zn/ sup 65/ is suitable for autoradiography; its gamma emission suggests its use in external counting. The usefulness of F/sup 18/ in the study of bones and teeth is limited by its short half-life ( approximates 110 min). However, by use of methods for rapid misolation and purification of F/sup 18/, combined with a rapid method for sectioning of whole frozen animals, it is possible to obtain excellent autoradiograms, demonstrating the isotope in bones and teeth. The bones take up F/sup 18/ within a few minutes following intravenous injection; this is mainly in the zones of mineralization; uncalcified cartilage shows no affinity for F/sup 18/ . The localization of Ra and Pu in bone mineral is described, and the use of Sg/ sup 35/, H/sup 3/, and C/sup 14/ labeled substances to investigate metabolism of organic constituents of bone is discussed. (BBB)
- Research Organization:
- Univ. of Chicago
- NSA Number:
- NSA-17-035420
- OSTI ID:
- 4670468
- Journal Information:
- Clin. Orthopaed., Vol. Vol: No. 24; Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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ANIMALS
BETA PARTICLES
BODY
BONES
CALCIUM
CALCIUM 45
CARBON 14
CARBONATES
COUNTERS
DISTRIBUTION
FLUORINE 18
GAMMA RADIATION
HALF- LIFE
LABELLED COMPOUNDS
MAGNESIUM 28
MAN
METABOLISM
MINERALS
MONKEYS
PHOSPHATES
PHOSPHORUS 32
PHYSIOLOGY
PLUTONIUM
RADIOAUTOGRAPHY
RADIUM
RARE EARTHS
SODIUM 22
SODIUM 24
SODIUM CHLORIDES
SOLUTIONS
STRONTIUM
STRONTIUM 85
TISSUES
TRITIUM
USES
YTTRIUM
ZINC 65