Comparative characteristics of the secretory responses of chromaffin and pheochromocytoma PC-12 cells to acetylcholine stimulation

Abstract

The molecular mechanisms of secretion in chromaffin cells possess many features similar to those of exocytotic neurotransmitter release in the synapses. It should be taken into account that chromaffin cells are formed from the precursor cells common to these units and neuronal elements. Numerous studies of the intracellular mechanisms of exocytosis showed that Ca ions are directly involved in this process [ 1-5]. Detailed experimental electrophysiological investigations of the secretion process using measurements o f the electrical capacity of the membrane demonstrated that this process includes two phases [6-8] and significantly depends on the intracellular Ca 2+ concentration. One of the possible explanations for such characteristics is the following: vesicles of different dimensions are involved in the exocytosis process. At low Ca 2+ concentrations, small vesicles similar to those in the synaptic terminals take part in exocytosis observed in chromaffin cells, while a progressive increase in the Ca 2+ concentration can result in exocytosis of the content of another, larger type of secretory vesicles [7, .9]. Our study aimed at determining specific features of the secretory responses of normal chromaffin cells and malignant cells of the pheochromocytoma PC-12 line;