Human pheochromocytoma cells studied in culture contain large amounts of DSIP-like material.

Delta sleep-inducing peptide (DSIP)-like immunoreactive (LI) material has been detected in nine different human pheochromocytoma tumors by immunocytochemistry. In primary tumors subjected to indirect immunofluorescence a variable number of tumor cells (25-75%) showed positive cytoplasmic labeling after incubation with DSIP antiserum. Tumor cells grown in culture were strongly labeled by the DSIP antiserum with DSIP-LI concentrated to cell bodies. Electron microscopic immunocytochemistry (immunogold labeling) of pheochromocytoma cells demonstrated DSIP-LI over the dense core of secretory granules. The presence of DSIP-LI in several HPLC fractions from conditioned culture media indicates secretion of DSIP-LI from cultured pheochromocytoma cells. The observations suggest that DSIP-LI is synthesized and stored in secretory granules before release. The different HPLC profiles from each of the tumors may reflect differences in processing or turnover of DSIP-LI in pheochromocytoma cells.