Effect of hydrocortisone, reserpine, propranolol and phentolamine on in vivo uptake of exogenous amines by adrenal chromaffin cells.

An autoradiographic study was performed on the effects of hydrocortisone, reserpine, propranolol and phentolamine on the uptake of tritiated amines by adrenal medullary cells of the mouse. Oral feeding of hydrocortisone ahd no significant effect on the normal uptake pattern of dopamine, noradrenaline or adrenaline by medullary cells of different type (A cells or NA cells) or location (marginal or central), although the overall amounts taken up were markedly reduced. Handling the animals led to similar reductions in the uptake of all three amines and was thus clearly shown to be the important factor in this effect. Reserpine reduced the uptake of [3H] noradrenaline to 25% of the control value although the relative distribution remained unchanged. Propranolol and phentolamine had no observed effect on [3H] noradrenaline uptake. These results are discussed in the light of the previously reported action of ACTH in reversing the effects of hypophysectomy on medullary amine uptake (Hirano and Kobayashi 1978), and it is concluded that ACTH must exert this effect directly on the adrenal medulla rather than through the secretion of adrenal corticosteroids. It is also suggested that reserpine acts, as in neurons, by blocking amine uptake into intracellular granules rather than by blocking uptake into the cell itself.