Release, storage and uptake of catecholamines by a clonal cell line of nerve growth factor (NGF) responsive pheochromocytoma cells

Abstract

Release, storage and uptake of catecholamines have been studied in cultures of a clonal line of rat pheochromocytoma cells designated as PC12. The PC12 line has previously been shown to respond to nerve growth factor (NGF) by extending neuronal-like processes and to synthesize and contain norepinephrine (NE) and dopamine (DA). In the present experiments, upon exposure to51.5mMK +, PC12 cells released a substantial proportion (ca. 30% and 12% for NGF-untreated and -treated cells, respectively) of their endogenous NE and DA. The release was dependent on the presence of Ca 2+ and was inhibited by excess Mg 2+. Veratridine, an alkaloid which activates Na + action potential ionophores, was also effective in releasing DA and NE. Exposure of PC12 cells (NGF-treated and -untreated) to reserpine (10 −5 M) resulted in depletion of intracellular DA and NE levels by over 90% in 21 h. PC12 cells were also found to take up NE from the external medium by means of a saturable transport mechanism which follows Michaelis-Menten kinetics (apparentK m≈ 2 μM), is energy and sodium dependent and which is blocked by low concentrations of cocaine and desmethylimipramine. Such findings indicate that PC12 cells (a) can release catecholamines by means of an exocytotic secretion mechanism, (b) store most of their endogenous catecholamines in chromaffin granules and/or vesicles and (c) have an uptake 1-type transport system for norepinephrine. PC12 cells thus appear to express a number of differentiated properties characteristic of sympathetic neurons and adrenal chromaffin cells and may be a useful system in which to study catecholamine metabolism.