AJP - Renal Physiology, Vol 250, Issue 2 302-F307, Copyright © 1986 by American Physiological Society
Effects of dietary alteration of bicarbonate and magnesium on rat bone
J. M. Burnell, C. Liu, A. G. Miller and E. Teubner
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.
