Alkaline lipase in rat intestinal mucosa: physiological parameters.

The present studies describe an alkaline active lipase in the rat intestinal mucosa. Alkaline lipase activity was determined using a glyceryl tri[14C]oleate emulsion at pH 8.0. Subcellular fractions were prepared from mucosal homogenates by differential centrifugation. Cells from villus to crypt were sequentially released using citrate and EDTA buffer. The enzyme was found to be most active in the proximal quarter of the intestine and in villus tips. Most of the activity was found in the cytosolic fraction. Bile salts stimulated the enzyme activity threefold. The presence of both Ca2+ and taurocholate was essential for optimal activity. Mucosal activity was greatly reduced on intraduodenal glyceryl trioleate infusion. Activity was restored when phosphatidylcholine was added to the glyceryl trioleate infusion. The fact that mucosal lipase has its greatest activity in the villus tips of the proximal intestine and in cytosol suggests that it may play an important role in mucosal glyceryltrioleate metabolism.