Localization of Carbonic Anhydrase XII to the Basolateral Membrane of H⁺-secreting Cells of Mouse and Rat Kidney

Abstract

S U M M A R YMembrane-associated carbonic anhydrase (CA) has a crucial role in renal HCO 3 Ϫ absorption. CA activity has been localized to both luminal and basolateral membranes of the tubule epithelial cells. CA XII is a transmembrane isoenzyme that has been demonstrated in the basolateral plasma membrane of human renal, intestinal, and reproductive epithelia. The present study was designed to demonstrate the distribution of CA XII expression in the rodent kidney. A new polyclonal antibody to recombinant mouse CA XII was used in both Western blotting and immunohistochemistry. Western blotting analysis revealed a 40-45-kD polypeptide in CA XII-expressing CHO cells and isolated membranes of mouse and rat kidney. Immunofluorescence staining localized CA XII in the basolateral plasma membranes of S1 and S2 proximal tubule segments. Abundant basolateral staining of CA XII was seen in a subpopulation of cells in both cortical and medullary collecting ducts. Double immunofluorescence staining identified these cells as H ϩ -secreting type A intercalated cells. The localization of CA XII in the peritubular space of proximal tubules suggests that it may play a role in renal HCO 3 Ϫ absorption, whereas the function of CA XII in the type A intercalated cells needs further investigation.

Expression of hypoxia‐inducible, membrane‐bound carbonic anhydrase isozyme XII in mouse tissues

“…Based on the present and previous (Kyllönen et al, 2003) results, kidney appears to contain the highest amount of CA XII. This is in line with the findings by Tü reci et al (1998) and Ivanov et al (1998), who showed high CA XII Fig.…”

“…Kidney served as a positive control for the reagents, which were used to demonstrate CA XII by immunofluorescence in the proximal tubules and in the intercalated cells of the collecting ducts (Kyllönen et al, 2003). This result is confirmed in Figure 2.…”

“…The production of polyclonal rabbit antibody raised against the recombinant mouse CA XII has recently been described by Kyllönen et al (2003). The specificity of the antibody was confirmed by Western blotting.…”

“…Some isozymes such as CA II are expressed in a number of different tissues, whereas others (e.g., CA VI, IX, and XIV) show a more limited distribution. It is notable, however, that all active isozymes are expressed in the alimentary tract, although the cellular localization is unique for each isozyme (Parkkila et al, 1994;Fleming et al, 1995;Sly and Hu, 1995;Parkkila, 1996, Pastoreková et al, 1997;Kivelä et al, 2000;Parkkila et al, 2003).…”

“…Immunohistochemical studies showed that CA XII protein is expressed in the human reproductive tissues, colon, and kidney (Karhumaa et al, 2000(Karhumaa et al, , 2001Parkkila et al, 2000). Kyllönen et al (2003) have recently studied the localization of CA XII in the mouse kidney and reported its localization in the proximal tubules and intercalated cells of the collecting ducts. This study was designed to investigate the expression of CA XII in other mouse tissues.…”