An Autoradiographic Study of the Mouse Carotid Body Using Tritiated Leucine, Dopa, Dopamine and ATP with Special Reference to the Chief Cell as a Paraneuron

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Abstract
A comparative autoradiographic study on the uptake and intracellular localization of 3H-leucine, 3H-dopa, 3H-dopamine and 3H-ATP derived radioactivity was performed in the mouse carotid body to investigate the metabolic features of the chief cell as a paraneuron. 3H-leucine derived radioactivity representing recently synthesized peptides was demonstrated in all kinds of cells in the carotid body and surrounding area. The chief cell was less radioactive than the nerve cell in the superior cervical ganglion. In EM autoradiography, no accumulation of radioactivity could be demonstrated either in the Golgi area of the chief cell, where the membrane-bound particles were probably formed, nor in the periphery of the cell, where they were stored before their release. Incorporation of 3H-dopa derived radioactivity representing recently synthesized catecholamines was specific to the chief cell, mast cell and nerve cell in the superior cervical ganglion. In the chief cell the distribution of radioactivity was roughly identical with that of the large dense-cored vesicles. Striking accumulations of 3H-dopamine derived radioactivity were demonstrated in the adrenergic nerve terminals in the perivascular space and the glomus complexes of the carotid body. Not all of the chief cells incorporated the 3H-dopamine derived radioactivity. 3H-ATP derived radioactivity was demonstrated in all kinds of cells in the carotid body and surrounding tissues. In the chief cell, as in other kinds of cells, the highest radioactivity was seen in the nucleus. If the large dense-cored vesicles and/or small synaptic vesicles in the chief cell, like those membrane-bound particles in other paraneurons, contain peptides, monoamines and ATP, the turnover of these products as secretory materials is apparently much slower in this cell than in such endocrine paraneurons as adrenal chromaffin cells and gut endocrine cells.