Abstract
The distribution of nucleoside phosphorylase activity was investigated in dog coronary blood vessels and in buffy coat preparations of circulating blood cells of the dog using a histochemical method. The enzyme activity was found in the cytoplasmic sap of endothelial cells, adventitial fibroblasts and fibrocytes, and in the axonal cytoplasm of the nerves. Smooth muscle and macrophages revealed no enzyme activity. Of the circulating blood cells, neutrophils, basophils, monocytes and platelets showed a uniform enzyme reaction, whereas eosinophils and erythrocytes apparently lacked activity. A part of the lymphocyte population reacted strongly while some lymphocytes were completely devoid of activity.