Morphologic and cytochemical properties of a clonal line of rat adrenal pheochromocytoma cells which respond to nerve growth factor

The PC12 pheochromocytoma line is a clonal line derived from a rat adrenal medullary tumor. PC12 cells grown in vitro have morphologic and cytochemical features in common with normal chromaffin cells in varying stages of development, and with human pheochromocytomas. These features include catecholamine stores demonstrable by formaldehyde-induced fluorescence and argentaffinic secretory granules, measuring 30 to 350 nm. Dark "norepinephrine"- and light "epinephrine"-type granules are both present, despite the absence of epinephrine and of its synthesizing enzyme, phenylethanolamine N-methyltransferase. Addition of nerve growth factor to the culture medium causes the cells to stop dividing and to develop neurite-like processes. Nerve growth factor-treated cells also develop clusters of 30- to 120-nm. granules and of 30- to 70-nm. granular and agranular vesicles, which resemble the granules and vesicles in adrenergic and cholinergic neurons and in neuroblastomas. In the early stages of process formation, formaldehyde-induced fluorescence can be demonstrated both in cell bodies and in processes. In later stages there is a marked diminution of formaldehyde-induced fluorescence in cell bodies and processes and a decreased number of granules in cell bodies, except in occasional cells within large clumps. These residual, fluorescent, granule-containing cells also remain argentaffinic. Alterations of the cell surface and of cytoplasmic filament arrangements also occur in cells treated with nerve growth factor. Further studies of the PC12 line may help to clarify relationships between morphology and function in the developing and mature autonomic nervous system, and the influence of nerve growth factor on these relationships.

Release of (3H)norepinephrine from a clonal line of pheochromocytoma cells (PC12) by nicotinic cholinergic stimulation

Release experiments were carried out in vitro with a clonal line of rat pheochromocytoma cells (designated PC12) which synthesize and store catecholamines and which, after treatment with nerve growth factor (NGF), cease cell division and extend neuronal-like processes. In the present study, PC12 cells were exposed to [3H]norepinephrine (NE) which they took up and stored in reserpine-sensitive sites. Exposure of such cells to nicotinic cholinergic agonists resulted in release of [3H]NE into the external medium. Release terminated within 1 min and partially returned after 20 min in the absence of agonist. After 1 min of stimulation with nicotine, NGF-treated cells released 5-6% of their contents of [3H]NE while NGF-untreated cells released 1-2%. Release from both NGF-treated and -untreated PC12 cells was inhibited in the absence of Ca2+ or by elevated Mg2+ and was blocked by the nicotinic antagonists D-tubocurarine and mecamylamine (50% inhibition at 0.1 and 0.06 micrometer, respectively). Release was not affected by the presence of tetrodotoxin. Such findings suggest that release of [3H]NE from PC12 cells may be mediated via stimulation of nicotinic acetylcholine receptors and a consequent stimulation-secretion coupling mechanism.

Ascorbic acid transport by a clonal line of pheochromocytoma cells

A clonal line of rat pheochromocytoma cells was used as a model of noradrenergic tissue to study ascorbic acid transport. These cells were used because, like sympathetic neurons, they synthesize large amounts of noradrenaline in the presence of ascorbate, they respond to nerve growth factor with the production of neurites and they release, store and take up catecholamines. In these cells, both with and without nerve growth factor (NGF) treatment, [14C]ascorbic acid was concentrated by a stereospecific saturable, energy dependent transport system that could be described by a Michaelis-Menten transport model. The Kt and Vmax for ascorbic acid were approximately 0.03 mM and 0.3 nmole per min per mg protein respectively for both untreated and NGF-treated cells. The ability of the cells to concentrate ascorbic acid was not due to intracellular binding. Cells untreated with NGF and loaded with [14C]ascorbic acid to a concentration of 5.6 nmoles per mg protein retained only 6% of the initial intracellular [14C]ascorbic acid after the 24 h in normal growth medium. Thus, although pheochromocytoma cells contain an ascorbate concentrating system, optimal production of noradrenaline requires ascorbate in the medium.

Specific neural and adrenal medullary antigens detected by antisera to clonal PC12 pheochromocytoma cells

Antisera were prepared against a clonal line (PC12) of rat pheochromocytoma cells that were grown in either the presence or the absence of nerve growth factor (NGF). PC12 cells respond to NGF by growing neurites and express many differentiated properties of adrenal chromaffin cells and sympathetic neurons. The antisera, after absorption with rat liver, kidney, spleen, and thymus, reacted in the micro-complement fixation and indirect immunofluorescence assays with PC12 cells (both NGF-treated and untreated), brain, adrenal medulla, and superior cervical ganglia, but not with a variety of other tissues. Cross-absorption of the antisera with brain and adrenal medulla indicated the presence of components that were specific to brain, adrenal medulla, and PC12 cells. Brain-specific and adrenal-medulla-specific antigens were also detected in other species, such as rabbit, cat, and mouse. No differences could be detected in the specificity of antisera raised against either NGF-treated or untreated PC12 cells. Indirect immunofluorescence on live cells also detected cell surface antigens on both cell bodies and processes. These results suggest that such antisera may be used to detect, localize, and identify specific neural and adrenal medullary antigens.

The binding properties and regional ontogeny of receptors for alpha-bungarotoxin in chick brain

The subcellular distribution, binding kinetics, pharmacologic properties and regional ontogeny of binding sites for alpha-[125I]bungarotoxins (alpha-[125I]BT) were studied in preparations of chick brain. Almost 95% of the specific binding was found in a 20,000 X g pellet. Two binding components were found, one with high (half-saturation at 1.5 X 10(-9) M) and another with low affinity for the toxin. The rate constants of association and dissociation of the toxin for the high-affinity site were found to be 3.5 X 10(4) M-1 - sec-1 and 3.8 X 10(-5) sec-1 (tau1/2 = 5.1 h, respectively). These data yielded a K alpha value of 1.1 X 10(-9) M. Nicotinic, but not muscarinic ligands were potent inhibitors of toxin binding at the high-affinity site. Thus, as in muscle, the binding site for toxin in chick brain appears to have the properties of a nicotinic acetylcholine (ACh) receptor. The ontogeny of the alpha-BT/ACh receptor was studied using homogenates of both whole brain and of discrete brain regions. In brain stem, optic lobe and cerebellum specific binding reached maximum levels in ovo and then decreased by maturity to values of 10,22 and 4.5 fmoles/mg protein, respectively. In contrast, whole brain and cerebral hemispheres reached plateau levels in ovo of 17 and 10 fmoles/mg protein, respectively. Major increases in total receptor number per region appeared in ovo between days 12 and 19 in brain stem and cerebellum, days 12 and 15 in optic lobes, and days 15 and 19 in hemispheres. The hemispheres were the only region to show a continued increase in total binding after hatching (3-fold increase by maturity). These findings are interpreted with respect to the development of chick brain and a model is suggested for the relationship between receptor ontogeny and neuronal differentiation and maturation.

Binding of alpha-bungarotoxin to chick sympathetic ganglia: properties of the receptor and its rate of appearance during developement

Studies were carried out on the binding of [125I]alpha-bungarotoxin (alphaBT) to membrane fragments of chick sympathetic ganglia. Specific binding of toxin was saturable with a KD of 1.1 nM. The rates of association and dissociation of the toxin from ganglionic membranes were 4.3 X 10(4) M-1 sec-1 and 4.6 X 10(-5) sec-1 (t 1/2 = 4.2 h). respectively. Binding was inhibited (by up to 95%) by low concentrations of nicotinic, but not by a muscarinic cholinergic ligand. The properties of the ganglionic binding site for alphaBT were consistent with its being a nicotinic acetylcholine receptor. The development of toxin receptors in chick ganglia was also studied. From days 7 to 11 in ovo, few receptors were present; from days 12 to 20 in ovo, there was a 10-fold increase in receptor number per ganglion; from hatching to maturity, the receptor number per ganglion slowly increased and reached a maximum of 14 fmoles. The ontogeny of receptors for alphaBT in sympathetic ganglia appears to correlate with the cytological maturation and innervation of the principal neurons.

Establishment of a noradrenergic clonal line of rat adrenal pheochromocytoma cells which respond to nerve growth factor

A single cell clonal line which responds reversibly to nerve growth factor (NGF) has been established from a transplantable rat adrenal pheochromocytoma. This line, designated PC12, has a homogeneous and near-diploid chromosome number of 40. By 1 week's exposure to NGF, PC12 cells cease to multiply and begin to extend branching varicose processes similar to those produced by sympathetic neurons in primary cell culture. By several weeks of exposure to NGF, the PC12 processes reach 500-1000 mum in length. Removal of NGF is followed by degeneration of processes within 24 hr and by resumption of cell multiplication within 72 hr. PC12 cells grown with or without NGF contain dense core chromaffin-like granules up to 350 nm in diameter. The NGF-treated cells also contain small vesicles which accumulate in process varicosities and endings. PC12 cells synthesize and store the catecholamine neurotransmitters dopamine and norepinephrine. The levels (per mg of protein) of catecholamines and of the their synthetic enzymes in PC12 cells are comparable to or higher than those found in rat adrenals. NGF-treatment of PC12 cells results in no change in the levels of catecholamines or of their synthetic enzymes when expressed on a per cell basis, but does result in a 4- to 6-fold decrease in levels when expressed on a per mg of protein basis. PC12 cells do not synthesize epinephrine and cannot be induced to do so by treatment with dexamethasone. The PC12 cell line should be a useful model system for neurobiological and neurochemical studies.

Neuronal properties of hybrid neuroblastoma X sympathetic ganglion cells

Clonal mouse neuroblastoma cells without tyrosine 3-monooxygenase [EC 1.14.16.2; tyrosine hydroxylase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating)] activity were fused with normal cells from embryonic mouse sympathetic ganglia. One of the 37 hybrid cell lines obtained possesses high tyrosine 3-monooxygenase activity and synthesizes dopamine. These cells also have excitable membranes and generate action potentials in response to electrical stimuli. Thus hybrid cells, generated by fusion of neuroblastoma cells with normal cells from the nervous system, can acquire neural properties not found with the parental neuroblastoma cells.