Observations on the localization of recently synthesized catecholamines in chromaffin cells after the injection of L-(2,5,6-3H)dopa.

The fate of tl-[2, 5, 6-3h] dopa, and the intracellular localization of its metabolic products dopamine, noradrenaline and adrenaline, have been determined by the simultaneous use of assay techniques following separation of amines by chromatography and light and electron microscopic autoradiography. During the first 24 h after i.v. or i.p. injection of [3H] DOPA, synthesis of the above catecholamines occurred. Throughout this time the labelled amines were associated with chromaffin granules or immediately adjacent cytosol and not with either the Golgi complex or rough endoplasmic reticulum. Labelling of chromaffin granules occurred simultaneously throughout the cell and there was no evidence of regions containing recently labelled granules and others containing previously charged (older) granules. Adrenaline-storing cells took up [3H] DOPA and its products more rapidly and lost recently synthesized adrenaline more rapidly than noradrenaline-storing cells took up and stored their equivalent amines. This was in keeping with a more rapid turnover of catecholamines in adrenaline-storing elements.