Expression of the transemembrane carbonic anhydrases, CA IX and CA XII, inthe human male excurrent ducts

Testicular fluid is concentrated and acidified during its passage through t he excurrent ducts. These processes involve bicarbonate absorption, in whic h carbonic anhydrases are implicated. In this study, the distribution of tw o transmembrane carbonic anhydrase isozymes (CA IX and CA XII) in the human excurrent ducts was investigated using isozyme-specific antibodies in conj unction with immunohistochemical and immunoblotting techniques. Specific st aining for CA XII was present in the basolateral plasma membrane of the epi thelial cells in the efferent ducts, predominantly in the non-ciliated cell s. In the epididymal duct, CA XII was detected only in sporadic cells, whic h also contained CA II, thus suggesting that they are apical mitochondria-r ich cells. CA IX was also localized to the basolateral plasma membrane of t he epithelium in the efferent ducts, but its staining was weaker and less u niform compared to CA XII, No signal for CA IX was detected in the epididym al duct. Western blot analysis from efferent duct samples revealed specific bands for CA IX and CA XII, confirming that the immunohistochemical staini ngs represent these isozymes, The expression of CA XII and CA IX in the exc urrent duct system and co-expression of CA XII with Aquaporin-1 in the same efferent duct epithelial cells suggest their functional involvement in ion transport and concentration processes of testicular fluid.