Localization of H(+)-ATPase and carbonic anhydrase II in ameloblasts at maturation.

The localization of vacuolar-type H(+)-ATPase and carbonic anhydrase II (CA II) in rat incisor enamel organs at maturation was examined by light and electron microscopy. The immunoreactivity for both vacuolar-type H(+)-ATPase and CA II was intense on the ruffled border of ruffle-ended ameloblasts (RA), but moderate at the distal end of smooth-ended ameloblasts (SA). Immuno-gold particles indicated that CA II was not confined to the ruffled border of RA alone, but also distributed in the cytoplasm of RA and SA. These findings suggest that RA may secrete protons produced by CA II via the ruffled border into enamel by active transport of vacuolar-type H(+)-ATPase. Secreted protons may activate hydrolytic enzymes to degrade the organic components of enamel matrix. Vacuolar-type H(+)-ATPase on vesicles of SA suggests that a specific configuration of ruffled borders in RA may be formed by the fusion of vesicle membranes in the distal end of cytoplasm of SA.