Uptake of catecholamines by a particulate fraction of the adrenal medulla.

Chromaffin granules isolated from beef adrenal medulla took up C(14)-labeled catecholamines from an isotonic medium at 37 degrees C at a rate approximately 20 times the rate at 0 degrees C. The uptake was stimulated three- to five-fold by Mg(++) and adenosine triphosphate. Reserpine (1 x 10(-5)M) caused a 90 percent inhibition of uptake; ethylenediaminetetraacetic acid completely inhibited the stimulation by magnesium and adenosine triphosphate, and the inhibition could be reversed by addition of excess Mg(++).