Immunohistochemical demonstration of extracellular carbonic anhydrase in epiphyseal growth cartilage

Summary The distribution of carbonic anhydrase isoenzymes C and B in the rat epiphyseal growth cartilage was demonstrated by an immunohistochemical method. The isoenzymes were found in different locations. Isoenzyme C was in the extracellular matrix of the hypertrophic and calcifying cartilage, and no reaction was observed in the chondrocytes. In contrast, the antiserum against isoenzyme B revealed only a weak cellular staining. This supports the hypothesis that carbonic anhydrase isoenzyme C, which is the high-activity form, changes the pH in the extracellular fluid of calcifying cartilage, favoring the deposition of calcium phosphate.