Identification of arterial and venous segments of blood vessels using alkaline phosphatase staining of ink/gelatin injected tissues.

The present study describes a method for discriminating between the arterial and venous segments of blood vessels in mouse tissues and organs using alkaline phosphatase (ALPase) staining of ink/gelatin injected tissues. Anesthetized mice were injected through the left ventricle with blue ink/gelatin, and various organs and tissues were removed from the body and fixed by immersion in 10% formalin. Sections 50-100 microm thick were incubated for ALPase in a medium containing naphthol AS-BI phosphate and fast red TR by the azocoupling method. In such specimens as the brain and skeletal muscles, ALPase activity was found in arterioles and capillaries on the arterial side, whereas it was absent in capillaries on the venous side and in venules. In the liver, only branches of the hepatic artery were positive. ALPase activity was absent in the vessels of the lung except for a positive reaction in branches of the bronchial arteries. These findings indicate that the ALPase activity is confined to the arterioles and arterial segments of the capillaries in the systemic circuit. Thus, ALPase staining of ink/gelatin injected specimens is a useful method for differentiating the arterial and venous segments of the micro-vascular bed in various organs and tissues in mice.