Immunoreactive calcitonin in catecholamine storage vesicles of human pheochromocytoma

The subcellular storage site for catecholamines in normal adrenal gland and pheochromocytoma tissue is the secretory granule or chromaffin granule (vesicle). Since some pheochromocytomas also contain calcitonin, we examined the occurrence and subcellular storage of calcitonin in 15 tumors from 12 patients with pheochromocytoma using a sensitive human calcitonin RIA. Only 1 of these patients had medullary thyroid carcinoma. The tumors of 9 patients contained calcitonin, from 1,705-3,602,457 pg/tumor. Highly purified chromaffin granules were prepared by sucrose density gradient centrifugation. The granules from 9 tumors in 8 patients contained calcitonin in amounts varying from 1,156-201,426 pg/tumor, accounting for 24 +/- 8% of the total calcitonin. Dilutions of chromaffin granule calcitonin immunoreactivity were parallel to the standard calcitonin RIA curve, which indicated antigenic similarity between pheochromocytoma calcitonin and synthetic human calcitonin; on gel filtration, chromaffin granule calcitonin coeluted with [125I]human calcitonin monomer, indicating size similarity. Thus, calcitonin seems to be present in the chromaffin secretory granules of most pheochromocytomas.