2 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 cell s was validated using the multidrug resistance gene (mdr I) product, P -glycoprotein, as marker for differentiated surface epithelial cells, Western blot analysis revealed a 6-fold higher expression level of P-g lycoprotein in colonic surface cells. K+-stimulated ouabain-insensitiv e ATPase activity was present in surface and in crypt cells, In surfac e cells, this K+-ATPase activity was only partly inhibitable by 10 mu M SCH 28080, while in crypt cells K+-ATPase activity equalled SCH 2808 0-sensitive ATPase activity, These results strongly suggest the presen ce of two distinct K+-ATPases in colonic epithetial cells. (C) 1995 Ac ademic Press. Inc.