Catecholamine transport and energy-linked function of chromafffin granules isolated from a human pheochromocytoma

The structure and function of chromaffin granules of human pheochromocytoma was extensively investigated in a highly purified granule fraction obtained from a single specimen of human pheochromocytoma tissue. Pheochromocytoma chromaffin granules were analyzed for catecholamine, ATP, enkephalin, phospholipid, cytochrome and ion content. Using a variety of techniques it was found that the membrane of these granules is highly impermeable to Na+, K+, and H+, and that the intragranular pH was maintained at 5.1 irrespective of suspending media. The presence of MgATP induces a transmembrane potential (delta psi) across the membrane of these granules which is positive inside and which corresponds to 90 mV. Both delta pH and delta psi are coupled to biogenic amine accumulation into the granules in a process which is reserpine sensitive. These properties are compared with those of chromaffin granules isolated from normal human tissue or from other animal species and are discussed in terms of possible explanation at a biochemical or subcellular level of the clinical manifestation of the pheochromocytoma.