Abstract
Summary Alkaline phosphatase activity has been investigated by histochemical methods in normal and diseased human large intestine. The tissues were constantly maintained at 4° C or below. Specimens were either frozen in liquid nitrogen, freeze-dried and embedded in glycol methacrylate for sectioning at 2 μ, or, fixed in ice-cold formol-calcium for frozen sectioning at 10 μ. The simultaneous coupling azo dye method using the substrates sodium α-naphthyl phosphate and Naphthol AS-BI phosphate, resulted in the demonstration of alkaline phosphatase activity in the surface epithelial cells, and the middle and upper crypts, of normal and transitional mucosa.