Calcium in bones

Alexander, G. V., Nusbaum, R.E. and MaeDonald, N.S. 1956 The relative retention of strontium and calcium in bone Tissae. Journal of Biological Chemistry 218 911-919. 

SA is known to accumulate in the body. It displaces calcium in bone matter and impacts the production of new blood cells in bone marrow. S A enters the bloodstream... 

Displaces calcium in bone matter Impacts production of new blood cells Damages liver and kidneys Shock... 

Toxicity—replaces calcium in bone, treatment of androgen-independent prostate cancer ... 

Some compounds, such as strontium chromate and strontium fluoride, are carcinogens and toxic if ingested. Strontium-90 is particularly dangerous because it is a radioactive bone-seeker that replaces the calcium in bone tissue. Radiation poisoning and death may occur in people exposed to excessive doses of Sr-90. Strontium-90, as well as some other radioisotopes that are produced by explosions of nuclear weapons and then transported atmospherically, may be inhaled by plants and animals many miles from the source of the detonation. This and other factors led to the ban on atmospheric testing of nuclear and thermonuclear weapons. 

Anonymous (2004). Role of calcium in bone building less than exercise. Available from http //www.foodnavigator-usa.com/news/news-ng.asp id=52720-role-of-calcium [Accessed November 2007]. 

S.G. Kshirsager, E. Lloyd, J. Vaughan, Discrimination between strontium and calcium in bone and the transferfrom blood to bone in the rabbit, Br. J. Radiol. 39 (1966) 131-140. 

Ypey DL, Weidema AF, Hold KM, Van der Laarse A, Ravesloot JH, Van Der Plas A, Nijweide PJ. 1992. Voltage, calcium, and stretch activated ionic channels and intracellular calcium in bone cells. J Bone Miner Res. 7 Suppl 2 S377-87. 

There are a few elements in these two groups that sometimes cause health problems because they are very similar to nearby elements. For instance, a toxic type of strontium can increase the risk of bone cancer and leukemia. Strontium, just one space below calcium in the table, is so similar to calcium that the body is sometimes fooled into absorbing it like calcium in bones and teeth. The similarities between elements can also be useful, as in the case of potassium chloride. People with high blood pressure and certain heart or kidney diseases need less sodium in their diets to stay healthy. Instead of sprinkling regular table salt or sodium chloride on their meals, they may use potassium chloride for a very similar salty taste. 

The structural role of calcium in bones and teeth is well known, but many proteins owe their structural integrity to the presence of metal ions that tie together and make rigid certain portions of these large molecules, portions that would otherwise be only loosely linked. Metal ions particularly known to do this are Ca2+ and Zn2+. 

Human bones frequently are well-preserved components at archaeological sites, and in many cases retain chemical constituents without exchange with the environment that contain information about diet (19-21). For example, ratios of strontium to calcium in bones indicate the relative importance of meat vs vegetable material in a diet. 

Substitutes for calcium in bones can be remobilized from bones, especially during pregnancy. 

A decrease in the rate of bone mineralization is a predictable effect of aging. For example, in infancy, the turnover rate of calcium in bone is 100% by adulthood, this turnover rate falls to only 18% per year. 

Vitamin D is used in the maintenance of plasma calcium ion concentrations. The normal level of free calcium ions in the plasma ranges from 1,0 to 1.5 mM. This concentration is needed to support a rxormal rate of deposit of calcium In bone during growth and during bone turnover. Apparently, vitamin D has no direct effect on the deposit of calcium ions in bone. It seems to act only indirectly and in maintaining plasma calcium at a level required to support bone mineralization. Note, however, that there remains interest in the possibility that vitamin D does have a direct effect on the cells that synthesize bone. A few details on bone formation and structure and on the vitamin D-dependent process of bone resorption are presented here. 

In patients with renal failure, the occurrence of conditioned zinc deficiency may be the result of a mixture of factors, which at present are ill defined. If 1,25-dihydroxycholecalciferol plays a role in the intestinal absorption of zinc, an impairment in its formation by the diseased kidney would be expected to result in malabsorption of zinc. It seems likely that plasma and soft tissue concentrations of zinc may be "protected in some individuals with renal failure by the dissolution of bone which occurs as a result of increased parathyroid activity in response to low serum calcium. In experimental animals, calcium deficiency has been shown to cause release of zinc from bone. In some patients who are successfully treated for hyperphosphatemia and hypocalcemia, the plama zinc concentration may be expected to decline because of the deposition of zinc along with calcium in bone. Thus, in the latter group in particular, a diet low in protein and high in refined cereal products and fat would be expected to contribute to a conditioned deficiency of zinc. Such a diet would be low in zinc. The patients reported by Mansouri et al. (37), who were treated with a diet containing 20-30 g of protein daily and who had low plasma concentrations of zinc, appear to represent such a clinical instance. Presumably the patients of Halsted and Smith (38) were similarly restricted in dietary protein. In other patients with renal failure whose dietary protein was not restricted, plasma zinc concentration were not decreased. Patients on dialysis had even higher levels, particularly... 

Remember that administering plicamycin (Mithracin) increases absorption of calcium in bone. 

Note Calcium is an essential component of bones, teeth, shells, and plant structures. It occurs in milk in trace amounts and is necessary in animal and human nutrition. Vitamin D aids in the deposition of calcium in bones. 

Bone serves as a vast reservoir of calcium in the body. Approximately 1 percent of calcium in bone can rapidly exchange with extracellular calcium ion. PTH stimulates demineralization of bone and release of calcium and phosphate into the blood by stimulating osteoclast formation and activity. This process is synergistically enhanced by vitamin D. 

The fact that strontium is chemically similar to calcium allows it to exchange for calcium in bone and other cellular compartments that are enriched in calcium. Many enzymes that are calcium-dependent will function when strontium is substituted, but changes in kinetic parameters may occur. As discussed in Section 3.5.1, strontium can interact with secondary cell messenger systems and transporter systems that normally use calcium. Furthermore, as described in Section 3.2.5 (Neurological Effects), synaptic transmission may be variably affected by strontium. Consequently, at high concentrations, differences in the chemical characteristics between strontium and calcium may be the basis for neurotoxic and neuromuscular perturbations associated with strontium intoxication. 

Calhoun NR, Campbell S, Smith JC. 1970. Accumulation of labeled zinc, strontium, and calcium in bone injuries. J Dent Res 49(5) 1083-1085. 

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