Two distinct K(+)-ATPase activities in rabbit distal colon.

The distribution of K(+)-ATPase activity in surface and crypt cells from rabbit distal colon was studied. Separation of surface and crypt cells was validated using the multidrug resistance gene (mdr 1) product, P-glycoprotein, as marker for differentiated surface epithelial cells. Western blot analysis revealed a 6-fold higher expression level of P-glycoprotein in colonic surface cells. K(+)-stimulated ouabain-insensitive ATPase activity was present in surface and in crypt cells. In surface cells, this K(+)-ATPase activity was only partly inhibitable by 10 microM SCH 28080, while in crypt cells K(+)-ATPase activity equalled SCH 28080-sensitive ATPase activity. These results strongly suggest the presence of two distinct K(+)-ATPases in colonic epithelial cells.