Abstract
Although many mast cells locate under the endothelial layer alond the sublobular veins in canine liver, the cell function remains to be fully defined.To establish the nature of the canine mast cell, the mast cells were examined by electron microscopy.A few monocytes contacted with luminal surface of endothelial cells under which mast cells situated.To confirm the chemotaxis of monocyte by hepatic mast cells, the hepatic venous vessels were treated with a histamine releaser(compound 48/80).The monocytes invaded into the subendothelial layer and extended their pseudopodium to the degranulated mast cells.It presumes that some mediators within the mast cell granules might act as a chemotactic substance to the monocyte.On the contrary, mast cells were migrating from subendothelial layer to venous lumen under normal condition.The migrating mast cell showed strong acid phosphatase reaction in their granules.It suggests that the granules of migrating mast cell became visible to acid phosphatase activity by a physical force such as contact stimulation, and that a part of mast cells remigrate from the venous wall to other places by the blood flow.Furthermore, hepatic mast cells were revealed to contain both endothelin−1 and histamine in their granules by immunocytochemistry.As these substances have an activity of stronger venous constriction, it seems that the mast cells play an important role in the blood flow regulation of the canine liver.
