Histochemical Demonstration of Carbonic Anhydrase Activity in the Odontogenic Cells of the Rat Incisor

Abstract

Aldehyde-fixed, EDTA-demineralized frozen sections of the rat maxillary incisor were histochemically stained for carbonic anhydrase activity, by use of Hansson's method. Intense staining was observed in the odontoblasts, all types of epithelial cells of enamel organ in the maturation zone, cementoblasts, and the cells of the lingual dental sac. Less intense but consistent staining was observed in all types of epithelial cells of odontogenic origin directly facing the pulp and pulp cells adjacent to the odontoblast cell layer in the apical part of the pulp, and was considered due to the carbonic anhydrase-catalyzed reaction. Staining of these cells was completely inhibited by heat pretreatment (120 degrees C, 30 min), 10(-6) mol/L acetazolamide in the incubation medium, incubation by continuous immersion under the liquid surface, and omission of the substrate, NaHCO3. The dentin also exhibited heavy staining which was inhibited by the heat pre-treatment. However, this dentinal staining resisted the inhibition by 10(-3) mol/L acetazolamide and was not inhibited by incubation by continuous immersion or incubation without the substrate NaHCO3. The dentinal staining was thus judged to have been due to non-enzymatic cobalt precipitation.

Immunohistochemical localization of carbonic anhydrase isozyme II in rat incisor epithelial cells at various stages of amelogenesis

“…Sugimoto et al (1988) have demonstrated CA activity in rat ameloblasts and papillary cells of the maturation stage histochemically, and their results agree with those described in the present study. Our immunohistochemical studies further confirmed that the CAII signal in these cells was constant until these cells fused with the gingival epithelium.…”

“…Hansson's histochemical procedure detects CA activity in tissues. This method has been used to localize CA in the rat incisor (Dogterom and Bronckers 1983;Sugimoto et al 1988), although it does not discriminate CA isozymes and its specificity has been questioned (Churg 1973;Lönnerholm 1984;Ridderstråle 1991). Our immunohistochemical observations were similar to the histochemical results.…”

“…To date, two studies concerning CA localization in rat enamel organ during the maturation stage have been reported (Sugimoto et al 1988;Lin et al 1994). Sugimoto et al (1988) have demonstrated CA activity in rat ameloblasts and papillary cells of the maturation stage histochemically, and their results agree with those described in the present study.…”

“…On the labial aspect of the rat incisor, CAII was observed in all types of epithelial cells of the enamel organ in the maturation zone and in the outer and inner dental epithelia near the apical loop. However, our immunohistochemical data did not demonstrate CAII reactivity in the pulp cells in the apical loop, in the presecretory ameloblasts that were more incisal than the posterior portion of ameloblasts facing the pulp, and in the odontoblasts on the labial aspect, as reported in the histochemical study of Sugimoto et al (1988). These cells may, however, contain other CA isozymes because the histochemical method demonstrates CA activity irrespective of its enzymatic form.…”

“…Biochemical assays have revealed CA activity in rodent tooth homogenates (Kondo and Kuriaki 1961;Dogterom and Bronckers 1983). Sugimoto et al (1988) demonstrated CA activity in the rat incisor by use of Hansson's histochemical method, which does not discriminate CA isozymes and the specificity of which has been questioned (Churg 1973;Lönnerholm 1984;Ridderstråle 1991).…”