Strontium biological function

Until now, no definitive proof has been provided of the essential functions of barium in plants, animals or man, though some clues for the biological functions of barium do exist. In 1949, Rygh fed rats with a semisynthetic diet which was depleted of barium, strontium, and zinc in all possible variations. The feeding with barium-depleted rations was found to cause a reduced lifespan, and also reduced the animals increase in body weight. However, no other investigations into barium depletion have been published. 

Schmahl W, Kollmer WE, Berg D, et al. 1979. Postnatal effects on Wistar rat pituitary morphology and function after application of strontium-90 on day 18 of pregnancy. Biological Implications of Radionuclides Released from Nuclear Industries. Proceeding of an International Symposium on Biological Implications 1 329-337. 

The cations Sr and Ba concentrate in the vertebrate skeleton, and the amounts of these elements vary as a function of mineral stmcture. In vivo, strontium has been found to accumulate in bone by exchange onto crystal surfaces, and is rapidly washed out after exogenous strontium is withdrawn (Dahl et al. 2001). Incorporation of strontium into the crystal lattice as a substitute of calcium occurs at a low level in vivo, in contrast to the extensive lattice substitution of strontium for calcium in fossil bone. Strontium is not easily washed out of subfossil bone (Tuross et al. 1989), and the uptake of strontium into biological apatite was once proposed as a potentially useful chronometer analogous to fluorine uptake (Turekian and Kulp 1956). The combined uptake of strontium and fluorine into vertebrate calcified tissue may in no small part account for the existence of a fossil record. Both of these elements stabilize biological apatite, and add substantially to the crystal stability of apatite under acidic conditions (Curzon 1988). 

Both strontium and barium are deposited as crystals in a range of organisms. These crystals may have both structural and functional properties. Some green algae such as the desmids deposit barium sulfate crystals, though it is unclear how much biological control is involved in the determination of the crystal structure which results [10]. 

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