Canadian Health&Care; Mall

The precise colocalization of subunit A with subunit E2 in apical microvilli and subapical vesicles is consistent with the assembly of these unique subunit isoforms to form the V-ATPase complex. This result indicates that clear cells use the A subunit for net luminal proton secretion in the epididymis. Both the ubiquitous isoform C1 and the more restricted C2 isoform were expressed in clear cells. Two C2 isoforms, C2a and C2b, resulting from alternative mRNA splicing, have been identified. C2a was detected in the lung and C2b in the kidney. In this study, an antibody that recognizes both C2a and C2b was used. We postulate that the C2 isoform that was recognized in epididymal clear cells is C2b because of the similarity between clear cells and kidney intercalated cells and because of the common embryological origin of the kidney and epididymis. Similarly, the ubiquitous G1 subunit isoform as well as the more restricted G3 isoform were detected in the apical pole of narrow and clear cells. G3 mRNA has been detected in the kidney, and its expression in epididymal clear cells could also be attributed to the fact that kidney and epididymis share the same embryological origin.