Changes in bone sodium and carbonate in metabolic acidosis and alkalosis in the dog

Metabolic acidosis and alkalosis were produced in adult dogs over 5- to 10-day periods. Midtibial cortical bone was analyzed for calcium, sodium, phosphorus, and carbonate. In acidosis bone CO(3)/Ca decreased 9.5% and bone Na/Ca decreased 6.3%. In alkalosis bone CO(3)/Ca increased 3.1% and bone Na/Ca increased 3.0%. Previous attempts to account for changes in net acid balance by summation of extra- and intracellular acid-base changes have uniformly resulted in about 40-60% of acid gained or lost being "unaccounted for." If it is assumed that changes in tibial cortex reflect changes in the entire skeletal system, changes in bone CO(3) (=) are sufficiently large to account for the "unaccounted for" acid change without postulating changes in cellular metabolic acid production.