STRONTIUM UPTAKE GEOLOGICAL, BIOLOGICAL AND MEDICAL ASPECTS

Strontium, stability in geological, biological and medical environments.

Strontium, Sr, a relatively abundant crustal element is used to test biochemical uptake in a variety of sites from different sources.. The contribution of Sr to living forms comes from its ability to substitute for calcium as noted in the hard tissues of invertebrates and vertebrates and in tree rings. The uptake of the radioactive 90Sr, a ß emitter with ½ life of 29 years, caused major anxiety as atmospheric fallout from above ground nuclear explosions in the 1950's. Sr sequestration in bioapatite of bones and teeth, could have accumulated in exposed children, but high levels of Sr partitioning into the mineral was minimized with adequate dietary Ca.

An ‘average 70 kg' human body contains 320 mg Sr although it is a non-essential nutrient. It arises from ingestion of e.g..onions (50 ppm Sr) or lettuce (74ppm Sr), at about 2 mg per day and is stored in the skeleton. Sr ranalate, a relatively new anti osteoporosis drug slowed the rate of demineralization of bone tissue in baboons Our investigations on mandibular bone and teeth in adult animals show 1) up to 2 % Sr in the alveolar bone surrounding the teeth depending on the intake dose 2) Sr in dentin scarcely above background, suggesing ‘exchange'. We conclude: Sr from the drug Sr- ranelate can become part of the mineral in mineralized tissues and may associate with previously formed mineral, an indication of the stability of the drug and the tissues. Testing employing 87/86 Sr will be reported.