LIGHT AND ELECTRON MICROSCOPIC STUDIES ON CHOLINESTERASE OF THE DOG HEART

Abstract

ChE activity in the canine heart was studied by light and electron microscopy by Karnovsky method.1. Sinus and atrioventricular nodes were stained most darkly in which numerous autonomic nerves and transitional cells showed most intense ChE activity.Atrioventricular bundle and the atrial septal muscle near the A-V node also showed intense staining. These atrial septal muscles, which show strong ChE activity, were identical to the internodal tracts and bypass tracts (James et al., 1966). The atrial and ventricular muscles showed very low ChE activity. The precipitation of reaction products grew larger in the specialized muscle cells, but those in ordinary cardiac muscle were small and fine.2. In P-cells, deposits of the reaction product were not great because sarcoplasmic reticulum and myofilaments were scarce.3. Papillary muscle showed the interesting figure of subendocardial dark ring after incubation in Karnovsky incubation medium. This thin layer is suspected to be a part of the conduction system.4. Intracardiac ganglia were often seen near the sinus node and sometimes at the peripheral region of the sinus node. All the ganglion cells studied were intensely positive for ChE activity.5. Although small cored vesicles in nerve terminals were rarely demonstrated in the present histochemical study, all the terminals which included the small cored vesicles were ChE negative.