Bone-resorption

Bone-resorption

Bone resorption depends on the secretion of proton and procathepsin L from osteoclasts into the extracellular lacunae. The proton is generated by carbonic anhydrase II in osteoclasts and activity in the lacunae by a proton pump driven by vacuolar-type H+-ATPase at the ruffled border, and the secreted proton participates in the bone resorption. However, the interrelated regulation between the proton and procathepsin L secretions from osteoclasts is still unclear. Addition of Bafilomycin A1, an H+-ATPase inhibitor, completely suppressed pit formation stimulated by PTH but did not suppress procathepsin L secretion.