Evidence for the presence of secondary calcium phosphate in bone and its stabilization by acid production.

Calvaria from three 4-day-old chicks were incubated in a variety of buffers to study the parameters controlling the equilibration of bone with its supporting fluid environment. Strong inferential chemical evidence was obtained for the presence in viable bone of some calcium phosphate phase of high solubility apparently governed by the Ksp of CaHPO4-2H2O. In dead bone, this phase underwent spontaneous conversion to a higher Ca/P ratio. In viable bone the soluble phase appeared to be stabilized by the metabolic production of acid (lactate) as revealed by the effects of selective inhibitors.