Search

Carotid bodies of dexamethasone-treated (daily injections, 10 days) adult male rats were analyzed with respect to catecholamine content and ultrastructure. Gas chromatographic-mass spectrometric assays demonstrated that norepinephrine (NE) and dopamine (DA) concentrations more than doubled after dexamethasone treatment. The increase in NE was relatively greater than that of DA. No epinephrine (E) could be detected. Morphometry revealed, as for the control carotid bodies, two subclasses of type I cells on the basis of the diameters of their dense-cored vesicles. These groups of cells were termed small vesicle cells (SVC) and large vesicle cells (LVC). Dexamethasone treatment resulted in significantly increased volume densities and diameters of the dense-cored vesicles in both SVC and LVC. The greatest increase occurred in the SVC. If these morphological changes do reflect the change in amine concentrations then it is possible to speculate that the type of cells with the greatest increase of amine storage capacity may store the kind of catecholamine most increased. Thus NE may presumably be stored in the SVC and DA in the LVC. Furthermore, these effects of administered glucocorticoids may also indicate a regulatory function for endogenous glucocorticoids on the carotid body catecholamines.

Gas chromatography-mass spectrometry makes possible the simultaneous measurement of norepinephrine and dopamine in concentrations of 0.1-milligram tissue samples. Specificity of the assay is confirmed both by the retention time of the compound and by the mass to charge ratio of the fragments recorded. The sensitivity is of the order of 0.5 picomole, and linearity of the response is maintained up to at least 200 picomoles.