ENHANCEMENT BY F-ACTIN OF MGATP-DEPENDENT DOPAMINE UPTAKE INTO ISOLATED CHROMAFFIN GRANULES

Interaction of chromaffin granules with the microfilament network in t he cytoplasmic space of adrenal medullary cells has been proposed, but the influence of chromaffin granule-microfilament interaction on gran ule function has not yet been studied. In the present study, the effec t of F-actin on dopamine uptake into isolated chromaffin granules was examined. The MgATP-dependent component of dopamine uptake was signifi cantly enhanced by F-actin. In contrast, catecholamine efflux from the granules was not significantly altered by F-actin under the condition s in which the enhancement of MgATP-dependent dopamine uptake was obse rved. These findings suggest that the interaction of chromaffin granul es with the microfilament network results in the enhancement of MgATP- dependent dopamine uptake into the granules, thus modulating the accum ulation and storage of catecholamines in the adrenal medullary cell.