Second Messenger Generation and Secretion in PC12 Cells. Role of Ca++ and Phosphoinositide Hydrolysis

PC12 is a line of neurosecretory cells originally developed by Greene and Tischler (1976) from a rat pheochromocytoma. This line has been extensively used in a number of laboratories around the world. Morphologically, growing PC12 cells resemble chromaffin cells of the adrenal medulla, although their secretion granules are smaller and less numerous (Greene and Tischler, 1976, 1982; Tischler and Greene, 1978; Watanabe et al., 1983). Because of this and other differences with respect to chromaffin cells, PC12 are now considered to be undifferentiated sympatoblasts. Their major catecholamine is dopamine, accumulated within secretory granules together with noradrenaline (Greene and Tischler, 1976, 1982; Rebois et al., 1980). Other neurotransmitters are synthesized in PC12 cells. Among these, acetylcholine is stored in organelles (not yet identified unambiguously), which are heavier than regular synaptic vesicles and lighter than the bulk of dopamine containing granules (Schubert et al., 1977). Peptides (enkephalins; neurotensin; Tischler et al., 1983; Panerai and Meldolesi, in preparation), as well as proteins typical of chromaffin and other secretory organelles (chromogranin A; secretogranin; Lee and Huttner, 1983) are present in PC12 cells, but their possible colocalization with dopamine has not been established with certainty yet.