CHOLINESTERASE AND LIPASE IN THE AMOEBOCYTES, INTESTINAL EPITHELIUM AND HEART MUSCLE OF THE QUAHOG, VENUS MERCENARIA

Abstract

1. Whole Venus heart homogenates hydrolyze acetylcholine and benzoylcholine at a low rate. 2. The enzymatic activity of such homogenates is the sum of that contributed by amoebocytes, intestinal epithelium and heart muscle. 3. Isolated amoebocytes hydrolyze acetylcholine and the enzyme responsible is inhibited by 10^-4 M physostigmine, thus indicating the presence of cholinesterase. 4. Recently developed histochemical procedures demonstrate serum cholinesterase and lipase in amoebocytes, intestinal epithelium and heart muscle. 5. Greatest lipase activity is present in the amoebocytes and intestinal epithelium, while serum cholinesterase activity is greatest in the ventricular muscle. 6. The potentiation of the action of acetylcholine on the isolated Venus heart by physostigmine is due to inhibition of serum cholinesterase in the amoebocytes and especially in the heart muscle. 7. The presence of varying levels of lipase in the intestinal epithelium of Venus lends support to the suggested presence of extracellular lipolytic enzymes in certain molluscs. 8. In Venus amoebocytes, another case is seen where cholinesterase activity is associated with structures which stain supravitally with Janus green B.