Abstract
The cellular and subcellular locialization of alkaline and K+-dependent phosphatase activities in the colonic mucosa of adult rats and rabbits was studied with the electron microscope. The 1-cysteine-sensitive alkaline phosphatase activity was observed in the brush border membrane of the chief cells. The contraluminal plasma membrane of chief cells was devoid of this enzyme activity. In contrast, the cardiac glycoside-sensitive K+-dependent phosphatase was predominantly localized in this region of the cheif cells.