Ph. Schlesinger et al., OSTEOCLASTIC ACID TRANSPORT - MECHANISM AND IMPLICATIONS FOR PHYSIOLOGICAL AND PHARMACOLOGICAL REGULATION, Mineral and electrolyte metabolism, 20(1-2), 1994, pp. 31-39
In order to solubilize bone mineral and degrade the organic matrix of
bone osteoclasts must secrete 1-2 protons for every Ca2+ liberated. Th
is transport is a major metabolic activity of osteoclasts requiring an
electrogenic H+-ATPase, a conductive chloride channel, a chloride-bic
arbonate exchanger, carbonic anhydrase, and functional/morphological p
olarization of the cell. The osteoclast H+-ATPase is electrically coup
led to a chloride channel in the ruffled membrane as are similar trans
port activities found in acidic intracellular vesicles, but the vanada
te sensitivity of the osteoclast proton pump is intermediated between
that of the E- and v-type proton pumps. The carbonic anhydrase and chl
oride-bicarbonate exchange provide an interface with pH regulation and
integrate bone resorption into systemic acid-base balance. With the m
olecular mediators of bone resorption being known we may consider the
control of bone resorption with an eye to mechanism and specificity th
at has not previously been possible. The effects of systemic acidosis
to increase bone resorption and the effects of carbonic anhydrase defi
ciency are consistent with our mechanism of osteoclast ion transport.