Useful cell lines derived from the adrenal medulla

Adrenal G Protein-Coupled Receptors and the Failing Heart: A Long-distance, Yet Intimate Affair

ABSTRACT

Systolic heart failure (HF) is a chronic clinical syndrome characterized by the reduction in cardiac function and still remains the disease with the highest mortality worldwide. Despite considerable advances in pharmacological treatment, HF represents a severe clinical and social burden. Chronic human HF is characterized by several important neurohormonal perturbations, emanating from both the autonomic nervous system and the adrenal glands. Circulating catecholamines (norepinephrine and epinephrine) and aldosterone elevations are among the salient alterations that confer significant hormonal burden on the already compromised function of the failing heart. This is why sympatholytic treatments (such as β-blockers) and renin-angiotensin system inhibitors or mineralocorticoid receptor antagonists, which block the effects of angiotensin II (AngII) and aldosterone on the failing heart, are part of the mainstay HF pharmacotherapy presently. The adrenal gland plays an important role in the modulation of cardiac neurohormonal stress because it is the source of almost all aldosterone, of all epinephrine, and of a significant amount of norepinephrine reaching the failing myocardium from the blood circulation. Synthesis and release of these hormones in the adrenals is tightly regulated by adrenal G protein-coupled receptors (GPCRs), such as adrenergic receptors and AngII receptors. In this review, we discuss important aspects of adrenal GPCR signaling and regulation, as they pertain to modulation of cardiac function in the context of chronic HF, by focusing on the 2 best studied adrenal GPCR types in that context, adrenergic receptors and AngII receptors (AT 1 Rs). Particular emphasis is given to findings from the past decade and a half that highlight the emerging roles of the GPCR-kinases and the β-arrestins in the adrenals, 2 protein families that regulate the signaling and functioning of GPCRs in all tissues, including the myocardium and the adrenal gland.

Anthracycline-induced cardiotoxicity: From pathobiology to identification of molecular targets for nuclear imaging

Anthracyclines are a widely used class of chemotherapy in pediatric and adult cancers, however, their use is hampered by the development of cardiotoxic side-effects and ensuing complications, primarily heart failure. Clinically used imaging modalities to screen for cardiotoxicity are mostly echocardiography and occasionally cardiac magnetic resonance imaging. However, the assessment of diastolic and global or segmental systolic function may not be sensitive to detect subclinical or early stages of cardiotoxicity. Multiple studies have scrutinized molecular nuclear imaging strategies to improve the detection of anthracycline-induced cardiotoxicity. Anthracyclines can activate all forms of cell death in cardiomyocytes. Injury mechanisms associated with anthracycline usage include apoptosis, necrosis, autophagy, ferroptosis, pyroptosis, reactive oxygen species, mitochondrial dysfunction, as well as cardiac fibrosis and perturbation in sympathetic drive and myocardial blood flow; some of which have been targeted using nuclear probes. This review retraces the pathobiology of anthracycline-induced cardiac injury, details the evidence to date supporting a molecular nuclear imaging strategy, explores disease mechanisms which have not yet been targeted, and proposes a clinical strategy incorporating molecular imaging to improve patient management.

GPCRs of adrenal chromaffin cells & catecholamines: The plot thickens

The circulating catecholamines (CAs) epinephrine (Epi) and norepinephrine (NE) derive from two major sources in the whole organism: the sympathetic nerve endings, which release NE on effector organs, and the chromaffin cells of the adrenal medulla, which are cells that synthesize, store and release Epi (mainly) and NE. All of the Epi in the body and a significant amount of circulating NE derive from the adrenal medulla. The secretion of CAs from adrenal chromaffin cells is regulated in a complex way by a variety of membrane receptors, the vast majority of which are G protein-coupled receptors (GPCRs), including adrenergic receptors (ARs), which act as "presynaptic autoreceptors" in this regard. There is a plethora of CA-secretagogue signals acting on these receptors but some of them, most notably the α2ARs, inhibit CA secretion. Over the past few years, however, a few new proteins present in chromaffin cells have been uncovered to participate in CA secretion regulation. Most prominent among these are GRK2 and β-arrestin1, which are known to interact with GPCRs regulating receptor signaling and function. The present review will discuss the molecular and signaling mechanisms by which adrenal chromaffin cell-residing GPCRs and their regulatory proteins modulate CA synthesis and secretion. Particular emphasis will be given to the newly discovered roles of GRK2 and β-arrestins in these processes and particular points of focus for future research will be highlighted, as well.

Adrenal G protein-coupled receptor kinase-2 in regulation of sympathetic nervous system activity in heart failure

Heart failure (HF), the number one cause of death in the western world, is caused by the insufficient performance of the heart leading to tissue underperfusion in response to an injury or insult. It comprises complex interactions between important neurohormonal mechanisms that try but ultimately fail to sustain cardiac output. The most prominent such mechanism is the sympathetic (adrenergic) nervous system (SNS), whose activity and outflow are greatly elevated in HF. SNS hyperactivity confers significant toxicity to the failing heart and markedly increases HF morbidity and mortality via excessive activation of adrenergic receptors, which are G protein-coupled receptors. Thus, ligand binding induces their coupling to heterotrimeric G proteins that transduce intracellular signals. G protein signaling is turned-off by the agonist-bound receptor phosphorylation courtesy of G protein-coupled receptor kinases (GRKs), followed by βarrestin binding, which prevents the GRK-phosphorylated receptor from further interaction with the G proteins and simultaneously leads it inside the cell (receptor sequestration). Recent evidence indicates that adrenal GRK2 and βarrestins can regulate adrenal catecholamine secretion, thereby modulating SNS activity in HF. The present review gives an account of all these studies on adrenal GRKs and βarrestins in HF and discusses the exciting new therapeutic possibilities for chronic HF offered by targeting these proteins pharmacologically.

In vitro models for neurotoxicology research

The nervous system has a highly complex organization, including many cell types with multiple functions, with an intricate anatomy and unique structural and functional characteristics; the study of its (dys)functionality following exposure to xenobiotics, neurotoxicology, constitutes an important issue in neurosciences.

Adrenergic nervous system in heart failure: pathophysiology and therapy

Heart failure (HF), the leading cause of death in the western world, develops when a cardiac injury or insult impairs the ability of the heart to pump blood and maintain tissue perfusion. It is characterized by a complex interplay of several neurohormonal mechanisms that become activated in the syndrome to try and sustain cardiac output in the face of decompensating function. Perhaps the most prominent among these neurohormonal mechanisms is the adrenergic (or sympathetic) nervous system (ANS), whose activity and outflow are enormously elevated in HF. Acutely, and if the heart works properly, this activation of the ANS will promptly restore cardiac function. However, if the cardiac insult persists over time, chances are the ANS will not be able to maintain cardiac function, the heart will progress into a state of chronic decompensated HF, and the hyperactive ANS will continue to push the heart to work at a level much higher than the cardiac muscle can handle. From that point on, ANS hyperactivity becomes a major problem in HF, conferring significant toxicity to the failing heart and markedly increasing its morbidity and mortality. The present review discusses the role of the ANS in cardiac physiology and in HF pathophysiology, the mechanisms of regulation of ANS activity and how they go awry in chronic HF, methods of measuring ANS activity in HF, the molecular alterations in heart physiology that occur in HF, along with their pharmacological and therapeutic implications, and, finally, drugs and other therapeutic modalities used in HF treatment that target or affect the ANS and its effects on the failing heart.

Physiology and pharmacology of the cardiovascular adrenergic system

Heart failure (HF), the leading cause of death in the western world, ensues in response to cardiac injury or insult and represents the inability of the heart to adequately pump blood and maintain tissue perfusion. It is characterized by complex interactions of several neurohormonal mechanisms that get activated in the syndrome in order to try and sustain cardiac output in the face of decompensating function. The most prominent among these neurohormonal mechanisms is the adrenergic (or sympathetic) nervous system (ANS), whose activity and outflow are greatly elevated in HF. Acutely, provided that the heart still works properly, this activation of the ANS will promptly restore cardiac function according to the fundamental Frank-Starling law of cardiac function. However, if the cardiac insult persists over time, this law no longer applies and ANS will not be able to sustain cardiac function. This is called decompensated HF, and the hyperactive ANS will continue to "push" the heart to work at a level much higher than the cardiac muscle can handle. From that point on, ANS hyperactivity becomes a major problem in HF, conferring significant toxicity to the failing heart and markedly increasing its morbidity and mortality. The present review discusses the role of the ANS in cardiac physiology and in HF pathophysiology, the mechanisms of regulation of ANS activity and how they go awry in chronic HF, and, finally, the molecular alterations in heart physiology that occur in HF along with their pharmacological and therapeutic implications for the failing heart.

Review of the history and current status of cell-transplant approaches for the management of neuropathic pain

Treatment of sensory neuropathies, whether inherited or caused by trauma, the progress of diabetes, or other disease states, are among the most difficult problems in modern clinical practice. Cell therapy to release antinociceptive agents near the injured spinal cord would be the logical next step in the development of treatment modalities. But few clinical trials, especially for chronic pain, have tested the transplant of cells or a cell line to treat human disease. The history of the research and development of useful cell-transplant-based approaches offers an understanding of the advantages and problems associated with these technologies, but as an adjuvant or replacement for current pharmacological treatments, cell therapy is a likely near future clinical tool for improved health care.

Protein phosphatase magnesium dependent 1A (PPM1A) plays a role in the differentiation and survival processes of nerve cells

The serine/threonine phosphatase type 2C (PPM1A) has a broad range of substrates, and its role in regulating stress response is well established. We have investigated the involvement of PPM1A in the survival and differentiation processes of PC6-3 cells, a subclone of the PC12 cell line. This cell line can differentiate into neuron like cells upon exposure to nerve growth factor (NGF). Overexpression of PPM1A in naive PC6-3 cells caused cell cycle arrest at the G2/M phase followed by apoptosis. Interestingly, PPM1A overexpression did not affect fully differentiated cells. Using PPM1A overexpressing cells and PPM1A knockdown cells, we show that this phosphatase affects NGF signaling in PC6-3 cells and is engaged in neurite outgrowth. In addition, the ablation of PPM1A interferes with NGF-induced growth arrest during differentiation of PC6-3 cells.

PHBV microspheres as neural tissue engineering scaffold support neuronal cell growth and axon-dendrite polarization

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) microspheres, with properties such as slower degradation and more efficient drug delivery properties, have important benefits for neural tissue engineering. Our previous studies have shown PHBV microspheres to improve cell growth and differentiation. This study aimed to investigate if PHBV microspheres would support neurons to extend these benefits to neural tissue engineering. PHBV microspheres' suitability as neural tissue engineering scaffolds was investigated using PC12 cells, cortical neurons (CNs), and neural progenitor cells (NPCs) to cover a variety of neuronal types for different applications. Microspheres were fabricated using an emulsion-solvent-evaporation technique. DNA quantification, cell viability assays, and immunofluorescent staining were carried out. PC12 cultures on PHBV microspheres showed growth trends comparable to two-dimensional controls. This was further verified by staining for cell spreading. Also, CNs expressed components of the signaling pathway on PHBV microspheres, and had greater axon-dendrite segregation (4.1 times for axon stains and 2.3 times for dendrite stains) than on coverslips. NPCs were also found to differentiate into neurons on the microspheres. Overall, the results indicate that PHBV microspheres, as scaffolds for neural tissue engineering, supported a variety of neuronal cell types and promoted greater axon-dendrite segregation.

Knockdown of dystrophin Dp71 impairs PC12 cells cycle: localization in the spindle and cytokinesis structures implies a role for Dp71 in cell division

The function of dystrophin Dp71 in neuronal cells remains to be established. Previously, we revealed the involvement of this protein in both nerve growth factor (NGF)-induced neuronal differentiation and cell adhesion by isolation and characterization of PC12 neuronal cells with depleted levels of Dp71. In this work, a novel phenotype of Dp71-knockdown cells was characterized, which is their delayed growth rate. Cell cycle analyses revealed an altered behavior of Dp71-depleted cells, which consists of a delay in G0/G1 transition and an increase in apoptosis during nocodazole-induced mitotic arrest. Dp71 associates with lamin B1 and β-dystroglycan, proteins involved in aspects of the cell division cycle; therefore, we compared the distribution of Dp71 with that of lamin B1 and β-dystroglycan in PC12 cells at mitosis and cytokinesis by means of immunofluorescence and confocal microscopy analysis. All of these three proteins exhibited a similar immunostaining pattern, localized at mitotic spindle, cleavage furrow, and midbody. It is noteworthy that a drastic decreased staining in mitotic spindle, cleavage furrow, and midbody was observed for both lamin B1 and β-dystroglycan in Dp71-depleted cells. Furthermore, we demonstrated the interaction of Dp71 with lamin B1 in PC12 cells by immunoprecipitation and pull-down assays, and importantly, we revealed that knockdown of Dp71 expression caused a marked reduction in lamin B1 levels and altered localization of the nuclear envelope protein emerin. Our data indicate that Dp71 is a component of the mitotic spindle and cytokinesis multi-protein apparatuses that might modulate the cell division cycle by affecting lamin B1 and β-dystroglycan levels.

Direct effect of dehydroepiandrosterone sulfate (DHEAS) on PC-12 cell differentiation processes

Dehydroepiandrosterone sulfate is classically seen as an inactive reservoir for the production of dehydroepiandrosterone. Steroid sulfatase is the enzyme that catalyzes the hydrolysis of dehydroepiandrosterone sulfate to dehydroepiandrosterone, which can then be further metabolized to other steroid hormones. Recent studies, however, indicate that dehydroepiandrosterone sulfate can mediate biological effects without being converted to dehydroepiandrosterone. This study aims to evaluate whether dehydroepiandrosterone sulfate itself influences the differentiation of PC-12 cells or if its desulfation to dehydroepiandrosterone is required. dehydroepiandrosterone and dehydroepiandrosterone sulfate both influence the differentiation of chromaffin PC-12 cells. Blocking steroid sulfatase activity and thereby the conversion of dehydroepiandrosterone sulfate to dehydroepiandrosterone by the enzyme blocker estrone sulfamate showed that the effect of dehydroepiandrosterone sulfate is independent of its conversion to dehydroepiandrosterone. Dehydroepiandrosterone sulfate, similar to dehydroepiandrosterone, reduced nerve growth factor-induced neurite outgrowth of PC-12 cells and the expression of synaptosomal-associated membrane protein of 25 kDa, increased the expression of chromogranin A and significantly increased dopamine release of PC-12 cells. In addition, dehydroepiandrosterone sulfate, dehydroepiandrosterone and membrane impermeable dehydroepiandrosterone-BSA all significantly reduced NGF-induced MAPK ERK1/2 signaling after 5 min. In summary, this study provides evidence that dehydroepiandrosterone sulfate, independent of its conversion to dehydroepiandrosterone, directs PC-12 cells' differentiation to a neuroendocrine direction. Furthermore, employing membrane-impermeable dehydroepiandrosterone-BSA indicates the involvement of plasma-membrane bound receptors.

Isolation of neural crest derived chromaffin progenitors from adult adrenal medulla

Chromaffin cells of the adrenal medulla are neural crest-derived cells of the sympathoadrenal lineage. Unlike the closely-related sympathetic neurons, a subpopulation of proliferation-competent cells exists even in the adult. Here, we describe the isolation, expansion, and in vitro characterization of proliferation-competent progenitor cells from the bovine adrenal medulla. Similar to neurospheres, these cells, when prevented from adherence to the culture dish, grew in spheres, which we named chromospheres. These chromospheres were devoid of mRNA specific for smooth muscle cells (MYH11) or endothelial cells (PECAM1). During sphere formation, markers for differentiated chromaffin cells, such as phenylethanolamine-N-methyl transferase, were downregulated while neural progenitor markers nestin, vimentin, musashi 1, and nerve growth factor receptor, as well as markers of neural crest progenitor cells such as Sox1 and Sox9, were upregulated. Clonal analysis and bromo-2'-deoxyuridine-incorporation analysis demonstrated the self-renewing capacity of chromosphere cells. Differentiation protocols using NGF and BMP4 or dexamethasone induced neuronal or endocrine differentiation, respectively. Electrophysiological analyses of neural cells derived from chromospheres revealed functional properties of mature nerve cells, such as tetrodotoxin-sensitive sodium channels and action potentials. Our study provides evidence that proliferation and differentiation competent chromaffin progenitor cells can be isolated from adult adrenal medulla and that these cells might harbor the potential for the treatment of neurodegenerative diseases, such as Parkinson's disease.

TRPM7 facilitates cholinergic vesicle fusion with the plasma membrane

TRPM7, of the transient receptor potential (TRP) family, is both an ion channel and a kinase. Previously, we showed that TRPM7 is located in the membranes of acetylcholine (ACh)-secreting synaptic vesicles of sympathetic neurons, forms a molecular complex with proteins of the vesicular fusion machinery, and is critical for stimulated neurotransmitter release. Here, we targeted pHluorin to small synaptic-like vesicles (SSLV) in PC12 cells and demonstrate that it can serve as a single-vesicle plasma membrane fusion reporter. In PC12 cells, as in sympathetic neurons, TRPM7 is located in ACh-secreting SSLVs. TRPM7 knockdown by siRNA, or abolishing channel activity by expression of a dominant negative TRPM7 pore mutant, decreased the frequency of spontaneous and voltage-stimulated SSLV fusion events without affecting large dense core vesicle secretion. We conclude that the conductance of TRPM7 across the vesicle membrane is important in SSLV fusion.

Plant phenolics regulate neoplastic cell growth and survival: a quantitative structure-activity and biochemical analysis

The anti-tumour activities of many plant phenolics at high concentrations (>100 micromol/L) suggest their potential use as dietary supplements in cancer chemoprevention and cancer chemotherapy. However, it is not clear what impact phenolic compounds have at the physiological concentrations obtained through consumption of high phenolic diets on neoplastic cells. In the present study, 54 naturally occurring phenolics were evaluated at physiologically relevant concentrations for their capacity to alter PC12 cell viability in response to serum deprivation, the chemotherepeutic agent etoposide, and the apoptogen C2-ceramide. Surprisingly, novel mitogenic, cytoprotective, and antiapoptotic activities were detected. Quantitative structure-activity relationship modelling indicated that many of these activities could be predicted by compound lipophilicity, steric bulk, and (or) antioxidant capacity, with the exception of inhibition of ceramide-induced apoptosis. Where quantitative structure-activity relationship analysis was insufficient, biochemical assessment demonstrated that the benzoate orsellinic acid blocked downstream caspase-12 activation following ceramide challenge. These findings demonstrate substantive mitogenic, cytoprotective, and antiapoptotic biological activities of plant phenolics on neoplastic cells at physiologically relevant dietary concentrations that should be considered in chemopreventive and chemotherapeutic strategies.

Primary culture of bovine chromaffin cells

This protocol describes the primary culture of individual chromaffin cells derived by enzymatic digestion from the adrenal medulla of the bovine adrenal gland. Since the late 1970s, such cells have provided a useful model system to study neurotransmitter biosynthesis, storage and release in the catecholaminergic system. The protocol can be divided into three stages: isolation of cells (4-6 h), determination of viable cell numbers (approximately 30 min) and growth in culture (3-7 d). An alternative procedure is to perform studies in a continuous chromaffin (pheochromocytoma) cell line, such as PC12, although such transformed cells are typically less highly differentiated than primary cells. The bovine chromaffin cell procedure should yield approximately 10-20 million cells, suitable for several experiments over the subsequent 3-7 d. Typical experiments involve transmitter biosynthesis, vesicular storage, exocytotic release, stimulus coupling (signal transduction) toward secretion or transcription, or morphology, including ultrastructure. The total time, from adrenal gland harvest until functional experiments, is typically 4-8 d.

Modulation of adrenal catecholamine secretion by in vivo gene transfer and manipulation of G protein-coupled receptor kinase-2 activity

We recently reported that the upregulation of adrenal G protein-coupled receptor kinase-2 (GRK2) causes enhanced catecholamine (CA) secretion by desensitizing sympatho-inhibitory alpha (2)-adrenergic receptors (alpha (2)ARs) of chromaffin cells, and thereby aggravating heart failure (HF). In this study, we sought to develop an efficient and reproducible in vivo adrenal gene transfer method to determine whether manipulation of adrenal GRK2 levels/activity regulates physiological CA secretion in rats. We specifically investigated two different in vivo gene delivery methods: direct injection into the suprarenal glands, and retrograde delivery through the suprarenal veins. We delivered adenoviral (Ad) vectors containing either GRK2 or an inhibitor of GRK2 activity, the beta ARKct. We found both delivery approaches equally effective at supporting robust (>80% of the whole organ) and adrenal-restricted transgene expression, in the cortical region as well as in the medullar region. Additionally, rats with AdGRK2-infected adrenals exhibit enhanced plasma CA levels when compared with control rats (AdGFP-injected adrenals), whereas plasma CA levels after Ad beta ARKct infection were significantly lower. Finally, in isolated chromaffin cells, alpha (2)ARs of AdGRK2-infected cells failed to inhibit CA secretion whereas Ad beta ARKct-infected cells showed normal alpha (2)AR responsiveness. These results not only indicate that in vivo adrenal gene transfer is an effective way of manipulating adrenal gland signalling, but also identify GRK2 as a critically important molecule involved in CA secretion.

Adrenal adrenoceptors in heart failure: fine-tuning cardiac stimulation

Chronic heart failure (HF) is characterized by sympathetic hyperactivity reflected by increased circulating catecholamines (CAs), which contributes significantly to its morbidity and mortality. Therefore, sympatholytic treatments, that is, treatments that reduce sympathetic hyperactivity, are being pursued currently for the treatment of HF. Secretion of CAs from the adrenal gland, which is a major source of CAs, is regulated by alpha(2)-adrenoceptors (alpha(2)ARs), which inhibit, and by beta-adrenoceptors (betaARs), which enhance CA secretion. All ARs are G-protein-coupled receptors (GPCRs), whose signaling and function are regulated tightly by the family of GPCR kinases (GRKs). Despite the enormous potential of adrenal ARs for the regulation of sympathetic outflow, elucidation of their properties has only begun recently. Here, recent advances regarding the roles of adrenal ARs in the regulation of sympathetic outflow in HF and the regulatory properties of ARs are discussed, along with the potential benefits and challenges of harnessing their function for HF therapy.

PC12 cells express IL-1 receptor type I and response to IL-1beta stimulation

PC12 cell line has been widely used in a diverse array of neurophysiological studies including in exploration of oxygen-sensing mechanism. In present study, we first identified with immunocytochemistry and Western blot methods that interleukin-1 receptor type I was expressed in the PC12 cells. We then demonstrated with patch clamping technique that extracellular application of IL-1beta dose-dependently inhibited the outward voltage-dependent and TEA-sensitive potassium currents (I(K)) in the PC12 cells, and pre-incubation with the interleukin-1 receptor antagonist almost completely abolished this inhibitory effect. In addition, application of IL-1beta shifted steady-state inactivation of I(K) in hyperpolarizing direction, but did not alter its steady-state activation. Furthermore, IL-1beta-induced inhibition of I(K) led to a membrane depolarization and a transient increase of [Ca(2+)](i) in PC12 cells. Taking together, the present study elucidates that PC12 cells bear interleukin-1 receptor and response to IL-1beta stimulation.

Down-regulation of Sox10 with specific small interfering RNA promotes transdifferentiation of Schwannoma cells into myofibroblasts

Neural crest-derived cells are noted for the long lasting plasticity during lineage commitment process and the potential for transdifferentiation into other neural crest derivatives. Schwann cells in particular have been reported to transdifferentiate into melanocytes and myofibroblasts. Detailed studies of transdifferentiation at the molecular level have been hampered by difficulty in isolating sufficient quantity of primary cells or cellular materials. Here, we describe a robust in vitro system in which Schwannoma cells undergo an apparent transdifferentiation into myofibroblasts. Importantly, we induce the transdifferentiation by down-regulating a single transcription factor, Sox10, thereby identifying a key molecular event in this process. Myofibroblasts thus generated showed carbachol-stimulated contraction and calcium transients and express several established myofibroblast-specific genes. These results suggest that generating desired cell types based on "knock-down" of critical genes may be a viable strategy.

Comparative studies of PC12 and mouse pheochromocytoma-derived rodent cell lines as models for the study of neuroendocrine systems

We have compared PC12 cell lines derived from different laboratories and the newly developed mouse pheochromocytoma (MPC) cell line. Morphologically, there were distinct differences in size, shape, adherence, and clumping behavior, which varied in response to different culture media, growth substrates, and nerve growth factor. Quantitative messenger ribonucleic acid (mRNA) analysis showed significant variability in the expression of the catecholaminergic biosynthetic enzymes tyrosine hydroxylase (TH), phenylethanolamine N-methyltransferase (PNMT), the noradrenaline transporter (NAT), and neuron-specific enolase (NSE) between all lines examined. Of most significance were the increased levels of PNMT mRNA in the MPC cells, which were to 15-fold greater than in the PC12 cell lines grown under the same conditions in Dulbecco modified Eagle medium (P < or = 0.05). Growth of MPC cells in Roswell Park Memorial Institute media induced a further significant increase in PNMT gene expression (P < or = 0.05). Immunohistochemistry for TH, PNMT, and NAT was generally consistent with mRNA analysis, with the MPC cells demonstrating strong immunoreactivity for PNMT. The MPC cells showed the highest levels of desipramine-sensitive [(3)H] noradrenaline uptake activity (threefold > than PC12 American Type Culture Center line, P < or = 0.05), despite relatively low levels of NAT mRNA. These results indicate that PC12 cell lines should be carefully chosen for optimal utility in the study of chromaffin cell or sympathetic neuron biology and that cell features will be influenced by type of media and substrate chosen. Furthermore, they confirm that the new MPC cell line is likely a useful model for the study of adrenergic mechanisms or studies involving NAT.