Immunohistocytochemical and immunofluorescent localization of catecholamine-synthesizing enzymes in the carotid body of the bat and dog.

By the immunoenzymatic PAP (peroxidase antiperoxidase) technique and immunofluorescent methods, the localization of a catecholamine-synthesizing enzyme, tyrosine hydroxylase (TH), in dopaminergic chief cells was elucidated in the dog and bat carotid bodies. Two types of cells were identified by PAP electron microscopy; TH-positive and TH-negative cells. The TH-positive reaction was observed both in the granules (about 170 and 300 nm in diameter) and in the ground substance, but not in the nucleus. Dopamine-beta-hydroxylase (DBH) reaction was negative in both cells. These findings may strongly suggest the presence of tyrosine hydroxylase not only in the cytoplasmic matrix but also in the granules in the dopaminergic cells of the carotid body.