Distribution of cholinesterase in canine venous system

Cholinesterase (ChE) activity was examined in 15 veins from dogs by pharmacological and histochemical procedures. Potentiation of acetylcholine (ACh)-induced contractile response by neostigmine was observed in helical and longitudinal strips of portal, mesenteric veins and middle segment of the inferior vena cava, but not in the other 12 veins. Histochemical studies with an electron-microscope (the method of Karnovsky-Roots) revealed that ChE activity was identified as high density granules around the smooth muscle cells only in the former three veins. The visible ChE activity was abolished by pretreatment with neostigmine.