Effects of dietary alteration of bicarbonate and magnesium on rat bone

Abstract

To study the effects of bicarbonate and magnesium on bone, mild acidosis and/or hypermagnesemia were produced in growing rats by feeding ammonium chloride and/or magnesium sulfate. Bone composition, quantitative histomorphometry, and mineral x-ray diffraction (XRD) characteristics were measured after 6 wk of treatment. The results demonstrated that both acidosis (decreased HCO3) and hypermagnesemia inhibited periosteal bone formation, and, when combined, results were summative; and the previously observed in vitro role of HCO3- and Mg2+ as inhibitors of crystal growth were confirmed in vivo. XRD measurements demonstrated that decreased plasma HCO3 resulted in larger crystals and increased Mg resulted in smaller crystals. However, the combined XRD effects of acidosis and hypermagnesemia resembled acidosis alone. It is postulated that the final composition and crystal structure of bone are strongly influenced by HCO3- and Mg2+, and the effects are mediated by the combined influence on both osteoblastic bone formation and the growth of hydroxyapatite.

Renal Control of Calcium, Phosphate, and Magnesium Homeostasis

“…Dietary magnesium restriction causes decreased bone magnesium content (97). Hypomagnesemia in rodents induces osteopenia with accelerated bone turnover, decreased bone volume, and decreased bone strength (98)(99)(100)(101). Although the bone magnesium stores are dynamic, the transporters that mediate magnesium flux in and out of bone have not yet been determined.…”

Molecular basis of epithelial Ca2+ and Mg2+ transport: insights from the TRP channel family

“…Evaluation of the chemical and mechanical properties of bone during hypomagnesaemia in the rat also revealed evidence of accelerated bone turnover, decreased bone volume, and decreased bone strength in Mg 2+ -depleted animals (Boskey et al 1992;Kenney et al 1994). Hence chronic hypomagnesaemia leads to severe osteopenia (Lai et al 1975;Burnell et al 1986). It is therefore likely that Mg 2+ is stored and exchanged with bone in a similar manner to Ca 2+ , and that chronic Mg 2+ depletion can affect bone resorption and formation.…”

Magnesium deficiency and osteoporosis: animal and human observations

“…It also binds to the surface of apatite crystals and retards their formation and growth [73,74]. When rats are fed excess Mg, the mineral crystals in their bones are smaller than those in control animals [75], whereas crystal size and perfection are significantly increased in Mg-deficient rats [10]. Postmenopausal women with osteoporosis and documented Mg deficiency were found to have larger and more perfect crystals in the trabecular bone as assessed on infrared spectrophotometry [76].…”