A PUTATIVE H+-K+-ATPASE IS SELECTIVELY EXPRESSED IN SURFACE EPITHELIAL-CELLS OF RAT DISTAL COLON

Recently a putative distal colon H+-K+-ATPase alpha-subunit has been identified and characterized (M. S. Crowson and G1. E. Shull. J. Biol. Chem. 267: 13740-13748, 1992). In the present study, we report the tissue and cell expression of this putative H+-K+-ATPase. The results indicate that, first, in the gut, the putative H+-K+-ATPase alpha-subunit is restricted to the distal part of the colon and is predominantly expressed in surface epithelial cells, in marked contrast to the alpha1-subunit of Na+-K+-ATPase that is also expressed in glands. These data suggest that the H+-K+-ATPase alpha-subunit is a potential marker for terminal differentiation of distal colon. Second, in the uterus, the putative H+-K+-ATPase is restricted to the region of the myometrium between the inner and midmuscular zone that is very rich in vascular supply and nerve cells. This striking expression suggests that the H+-K+-ATPase may not be involved in the control of pH and potassium concentration of the uterine fluid but rather in distinct functions of vascular and/or nerve cells. Third, with the use of three independent and different approaches (Northern blot analysis, ribonuclease protection assay, and in situ hybridization), we were unable to detect any significant amount of H+-K+-ATPase transcripts in kidney tissue. Our data suggest that the putative distal colon H+-K+-ATPase is probably distinct from the kidney isoform. Finally, we report the sequence of a set of degenerate oligonucleotides that are useful to clone alpha-subunits of the Na+-K+-/H+-K+-ATPase gene family in different tissues and different species.