Abstract
Dissociated cells from a human pheochromocytoma tumor were maintained in culture, and the secretion of opioid peptides (OP), endogenous catecholamines (CA) and preloaded [ 3H] norepinephrine from these cells was examined. Nicotine, veratridine, barium or Ionomycin stimulated the secretion of OP, endogenous CA and 3H from the pheochromocytoma cells. In general, the different secretagogues were more potent in releasing OP than endogenous CA; 3H secretion was intermediate. Secretion of OP was more sensitive to stimulation by the calcium ionophore Ionomycin and by veratridine than was CA secretion. Nicotine-evoked OP secretion was more sensitive to extracellular calcium concentration than was secretion of CA or 3H. In contrast, bovine adrenal chromaffin cells show no such differential secretion of OP and CA in response to Ionomycin stimulation or to nicotine stimulation under conditions of varying extracellular calcium concentration. The results show that human pheochromocytomas secrete OP as well as CA and that there may be heterogeneous storage pools of CA and OP in cultured pheochromocytoma cells.
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