Ultrastructural histochemistry of carbonic anhydrase in rat osteoclasts

Carbonic anhydrase (CA) was localized in osteoclasts of rat tibial metaphysis by light and electron microscopy using the histochemical method of Hansson. Ultrastructurally, positive staining was seen in the cytosol, mitochondrial cristae, Golgi apparatus, some nuclei and lysosomelike vesicles, and on the bone surface beneath the osteoclast. The presence of the enzyme within the Golgi ++apparatus, lysosomelike vesicles, and on the bone surface beneath the osteoclast suggests that some CA may be secreted into the resorbing zone. According to literature, the above localization of CA suggests that there may be three isozymes of CA in the rat osteoclast. These are ubiquitous cytosolic CA (CA-II), mitochondrial CA (CA-V) and secretory CA (CA-VI).