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At least 19 recordsLinked to original sources
PubMed1991

Morphological differentiation of rat pheochromocytoma cells (PC12 cells) by electric stimulation.

The effects of electric stimulation on the morphological differentiation of PC12 cells are described. PC12 cells were stimulated with the 'theta' (4-7 Hz electroencephalogram (EEG) rhythm) pattern-electric stimulation, which was known to elicit stable long-term potentiation (LTP) in the CA1 region of the hippocampus. The stimulation induced the neurite outgrowth of PC12 cells, as well as nerve growth factor (NGF). This result suggests that the electric signal has a differentiating potential equivalent to the receptor-ligand interaction.

Animals↗
PubMed1994

Rapid sprouting of filopodia in nerve terminals of chromaffin cells, PC12 cells, and dorsal root neurons induced by electrical stimulation.

Rapid morphological changes induced by direct electrical stimulation of nerve terminals were studied by using video-enhanced differential interference contrast microscopy at a very high magnification (12,000x). We used mainly cultured bovine chromaffin cells, which developed neurite-like processes, and PC12 cells, which showed neuronal differentiation upon NGF treatment. In a few cases, primary neurons of the rat dorsal root ganglion were also examined. Brief pulse stimulation of the terminals and varicosities induced exocytosis accompanied by rapid formation of filopodia. These filopodia, 0.1-0.2 micron in diameter and up to 10 microns in length, formed within a few hundreds of milliseconds and then retracted within tens of seconds. They could also be induced by K depolarization. This rapid filopodial sprouting strongly depended on the presence of extracellular Ca2+ and could be abolished in a medium containing a Ca chelator (EGTA) or La2+. Anti-cytoskeletal agents colchicine and cytochalasin B failed to block this response completely but lidocaine fully suppressed it. Quantitative analysis of exocytosis and filopodial sprouting showed that they were independent events, not directly linked to each other, having different thresholds usually higher for filopodial formation. In PC12 cells, the extent of filopodial sprouting varied with the state of differentiation of the cells, suggesting a functional role of rapid sprouting during a particular phase of their differentiation. Filopodia could be induced with greater ease by repetitive stimulation. The same responses may occur at growth cones approaching the target cells or even at mature synapses particularly after repetitive electrical activity, possibly playing a role in use-dependent synapse formation or plasticity.

Aging↗
PubMed1997

Effects of oxidative stress on prion protein expression in PC12 cells.

PC12 cells are known to express the prion protein, a normal cell surface glycoprotein. This protein is upregulated in PC12 cells differentiated with nerve growth factor. A neurotoxic prion protein peptide, PrP106-126, is not toxic to PC12 cells alone. PrP106-126 is toxic to PC12 cells co-cultured with microglia and more so to NGF-differentiated PC12 cells. PC12 cells selected for resistance to either copper toxicity or oxidative stress have higher levels of PrP(C) expression. Both PC12 variants are more sensitive to the toxicity of PrP106-126. This suggests that PC12 sensitivity to PrP106-126 toxicity is related to prion protein expression and not to a state of high differentiation induced by NGF. Variants of PC12 cells that are more resistant to copper toxicity have higher levels of anti-oxidant enzymes, superoxide dismutase and glutathione peroxidase. Our results suggest that cells expressing higher levels of PrP(C) have higher resistance to oxidative stress or copper toxicity but are more sensitive to PrP106-126 toxicity. Prion protein expression may be involved in both the metabolism of copper and resistance to oxidative stress. Increased cellular resistance to copper toxicity may be partly related to increased activity of anti-oxidant enzymes.

Animals↗
PubMed1997

Need for caspases in apoptosis of trophic factor-deprived PC12 cells.

PC12 cells are a useful model system for studying neuronal apoptosis. Like neurons, they undergo apoptosis when deprived of trophic support. Involvement of caspases [interleukin 1beta-converting enzyme (ICE)-related proteases] has been implicated in apoptosis induced by various stimuli in many cell types, including neurons. In the present study we investigated the need for caspases participation in apoptosis induced by growth factor deprivation in naive and neuronal PC12 cells. For this purpose we generated PC12 cell lines that consistently express the viral caspases inhibitor genes p35 or crmA, and analyzed their susceptibility to trophic factor deprivation. We also examined the effects of cell-permeable peptide inhibitors of caspases. Our results showed that broad-spectrum inhibitors of the caspases, namely the baculovirus p35 gene and the peptide benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, effectively inhibit the death of both naive and neuronal PC12 cells. However, caspase-1 (ICE)-specific inhibitors, namely the peptides Ac-Try-Val-Ala-Asp-chloromethylketone and Ac-Try-Val-Ala-Asp-aldehyde, as well as crmA, were much less effective. These findings demonstrate that caspases, but not caspase-1, are needed for apoptosis induced by trophic factor deprivation in both naive and neuronal PC12 cells. Northern and Western blot analyses showed that PC12 cells express caspase-3. We therefore examined the involvement of caspase-3 in the death process of trophic factor-deprived PC12 cells. Our results showed that the pro-caspase-3 and its substrate poly-(ADP-ribose) polymerase are cleaved at similar rates in serum-deprived PC12 cells. Moreover, cell lysates prepared from these cells possess caspase-3-like activity, as determined by their ability to cleave the fluorogenic peptide substrate Ac-Asp-Glu-Val-Asp-7-amino-4-methylcoumarin. These findings strongly suggest that caspase-3 or caspase-3-like proteases are activated in trophic factor-deprived PC12 cells.

Amino Acid Chloromethyl Ketones↗
PubMed1998

Neurotoxicity of 25-OH-cholesterol on NGF-differentiated PC12 cells.

PC12 cells induced to differentiate with nerve growth factor were used to study the neurotoxicity of 25-OH-cholesterol. This agent induced a dose- and time-dependent cell death in neuronal PC12 cells. Cells treated with this agent showed condensed nuclei, a morphology similar to that of cells dying of programmed cell death. However, agents known to prevent neuronal programmed cell death (cyclic AMP, KCl, aurintricarboxylic acid, and cycloheximide) failed to prevent the 25-OH-cholesterol-mediated cytotoxicity. On the other hand, cell death induced by 25-OH-cholesterol was prevented by treatment with vitamin E and methyl-beta-cyclodextrin. In contrast to observations made in other cell types, whole-cell patch clamp recording of neuronal PC12 cells revealed that treatment with 25-OH-cholesterol did not significantly alter calcium influx through voltage-dependent channels. These results provide the first characterization of the toxicity of cholesterol oxides toward neuronal PC12 cells, which should be useful in future studies on the interactions between cholesterol oxides and cells from the nervous system.

Animals↗
PubMed1993

Nerve growth factor-induced neuronal differentiation is accompanied by differential induction and localization of the amyloid precursor protein (APP) in PC12 cells and variant PC12S cells.

PC12 cells and the morphological variant PC12S cells in culture were examined by immunochemical methods for the presence of the amyloid precursor protein (APP), before and after treatment with the nerve growth factor (NGF). In untreated PC12, untreated PC12S and in NGF-treated PC12 cells, APP was localized in the cytoplasm, whereas in NGF-treated PC12S cells, APP was localized at growth cones, processes and cytoplasm. In PC12 cells, three major forms of APP (695 and 751/770) were detected by Western blot. After NGF treatment, only the level of APP 695 was increased. Immunoprecipitation studies in PC12 cells revealed six protein species, corresponding to immature and mature forms of each of the three APP 695, 751 and 770 proteins. Addition of NGF increased the synthesis of the immature and mature forms of APP695. In PC12S cells, only the higher molecular weight forms of APP (751/770) were detected by both Western blot and immunoprecipitation. Addition of NGF had no effect on their levels. In both cell types, the level of the secreted form of APP showed a significant transient increase after NGF treatment. These results suggest that NGF can differentially regulate the molecular forms of APP and the localization of APP within the cell.

Amyloid beta-Protein Precursor↗
PubMed1997

Down-regulation of adenosine A2A receptors upon NGF-induced differentiation of PC12 cells.

PC12 cell differentiation was induced by one week of nerve growth factor (NGF) treatment and adenosine A2A receptor expression and activity were analysed. Undifferentiated PC12 cells expressed very high levels of adenosine A2A receptors (approximately equal to 2 pmol/mg) and exhibited strong cyclic AMP (cAMP) responses when stimulated with the selective adenosine A2A receptor agonist 2-[p-(2-carbonylethyl) phenylethylamino-5'-N-ethylcarboxamidoadenosine]. NGF-induced differentiation was accompanied by a down-regulation of adenosine A2A receptors: receptor binding decreased to 500 fmol/mg, immunoreactive A2A receptor protein was decreased by about half and cAMP production was reduced by 60%. In situ hybridization experiments demonstrated a heterogenous distribution of A2A receptor mRNA and a decreased number of strongly labelled cells after NGF treatment. Stimulation of the cells with the non-selective adenosine receptor agonist N-ethylcarboxamidoadenosine (NECA) inhibited NGF-induced mitogen-activated protein kinase activation. These results thus show that NGF-induced differentiation of PC12 cells is accompanied by a decrease in A2A receptor-mediated cAMP accumulation. This might be a way for PC12 cells to counteract an inhibitory effect of A2A receptor activation on some aspects of neurotrophin signalling.

Animals↗
PubMed1995

Characterization of synaptic vesicles and related neuronal features in nerve growth factor and ras oncogene differentiated PC12 cells.

PC12 cells can differentiate into neuron-like cells after treatment with either nerve growth factor (NGF) or transduction with a retrovirus which expresses the K-ras oncogene. The concomitant treatment of NGF plus ras differentiates PC12 cells further than either agent alone with respect to neurite outgrowth, acetylcholinesterase levels, and most strikingly, the number of synaptic vesicle (SV) clusters. These SV clusters in PC12 cell neurites closely resemble those in the presynaptic terminals of neurons. Such SV clusters have not been described in cell lines previously. The SV clusters from all three differentiated groups (NGF, ras, and NGF plus ras) were similar in size, shape, and configuration, except that the ones in the doubly treated group occur in higher frequency and have more vesicles. The synaptic nature of these vesicle clusters was demonstrated by their regulated depletion after potassium stimulation. Furthermore, these vesicle clusters stained positively for two SV-associated proteins, synapsin I and synaptophysin, by EM immunocytochemistry (ICC). Such SV clusters in a cell line are very useful for characterizing the regulated release of SVs and the distribution of SV-related antigens in intact cells. Analysis by SDS-gel electrophoresis and immunoblotting indicated that synapsin I levels are higher in all three differentiated groups compared to untreated cells; whereas synaptophysin levels are lower in cells exposed to NGF alone or with NGF and ras double treatment. Possible convergence and/or divergence on the mechanisms of NGF and ras differentiation in PC12 cells are discussed.

Acetylcholinesterase↗
PubMed1999

Characterization of myosin V from PC12 cells.

PC12 cell line is a cellular model to study neurite outgrowth and neurotransmitter release mechanisms. Molecular motors may be involved in these responses and myosin V could be a candidate to mediate these effects. Overlay experiments using [(125)I]-calmodulin showed that PC12 cells possess several calmodulin-binding proteins, some of them around 190-210 kDa. Western blots using affinity purified polyclonal antibodies raised against chicken brain myosin V revealed a component of 190 kDa, a molecular mass typical of myosin V. Furthermore, Northern blots using a myosin V probe also detected a transcript of around 12 kbp. Immunofluorescence cytochemistry demonstrated the localization of myosin V throughout the cytoplasm, in the neurites, growth cone tips, and with an intense asymmetrical perinuclear labeling. Western blot analyses of PC12 cellular extracts after FGF-2 and/or dibutyryl cAMP treatment revealed variations between myosin V and myosin II expression during neuronal differentiation. These results demonstrated the presence of myosin V in PC12 cells and also suggest a role for this motor molecule in the neuronal differentiation response in PC12 cells.

Animals↗
PubMed1998

Genetic elements regulating HES-1 induction in Wnt-1-transformed PC12 cells.

PC12 cells differentiate in response to nerve growth factor from a chromaffin cell to a sympathetic neuronal phenotype. Wnt-1 is a secreted signaling factor required for development of mammalian midbrain and cerebellum. PC12 cells transformed by Wnt-1 fail to express several differentiation-specific genes in response to nerve growth factor. We have previously shown that HES-1, a negative regulator of neuronal differentiation, is increased in Wnt-1/PC12 cells (P. S. Issack and E. B. Ziff. Altered expression of helix-loop-helix transcriptional regulators and cyclin D1 in Wnt-1-transformed PC12 cells. Cell Growth & Differ., 9: 837-845). Here, we show that the HES-1 promoter is more active in Wnt-1/PC12 cells relative to PC12 and that the binding sites for the transcription factor RBP-J kappa contribute to this induction. We also identify two additional promoter elements required for elevated HES-1 expression. One element binds Wnt-1-induced protein complexes in a sequence-specific manner. Identification of Wnt-1 responsive elements in potential target genes may provide clues to nuclear pathways regulated by Wnt-1.

Animals↗
PubMed1999

Activation of stress-activated protein kinases correlates with neurite outgrowth induced by protease inhibition in PC12 cells.

PC12 cells are well characterized for their ability to differentiate into neuronal-like cells when challenged with nerve growth factor. It has been reported that the calpain and proteasome inhibitor N-acetyl-Leu-Leu-norleucinal (CI) is also able to induce neurite outgrowth in PC12 cells. In this study, we report that the inhibitor of proteasomal chymotrypsin-like activity, carbobenzoxy-Ile-Glu-(O-tert-butyl)-Ala-Leu-aldehyde (PSI), can also induce differentiation of PC12 cells. Induction of neurite outgrowth with PSI, CI, or its close analogue, carbobenzoxy-Leu-Leu-leucinal (MG132), was associated with stress-activated protein kinase (SAPK) activation. Neurite formation induced by protease inhibition was independent of mitogen-activated protein kinase/extracellular signal-regulated kinase, p38/reactivating kinase, or phosphatidylinositol 3-kinase activities. The exact mechanism by which protease inhibition activates SAPKs remains to be elucidated; however, our results suggest that the SAPK signal transduction cascade may be an alternative and/or parallel pathway in the regulation of neuronal differentiation.

Animals↗
PubMed1993

Regulated and constitutive secretion of distinct molecular forms of acetylcholinesterase from PC12 cells.

PC12 cells secrete the enzyme acetylcholinesterase (AChE) while at rest, and increase the overall rate of this secretion 2-fold upon depolarization. This behavior is different from the release of other markers by the constitutive or regulated secretory pathways in PC12 cells. Both the resting and stimulated release of AChE are unchanged after treatment with a membrane-impermeable esterase inhibitor, demonstrating that it represents true secretion and not shedding from the cell surface. The stimulation release of AChE is Ca(2+)-dependent, while the unstimulated release is not. Analysis of the molecular forms of AChE secreted by PC12 cells indicates that the release of AChE actually involves two concurrent but independent secretory processes, and that the G4 form of the enzyme is secreted constitutively, while both the G2 and G4 forms are secreted in a regulated manner, presumably from regulated secretory vesicles. Compared with other regulated secretory proteins, a much smaller fraction of cellular AChE is secreted, and the intracellular localization of this enzyme differs from that of other regulated secretory proteins. The demonstration that a cell line that exhibits regulated secretion of acetylcholine (ACh) is also capable of regulated secretion of AChE provides additional evidence for the existence of multiple regulated secretory pathways within a single cell. Moreover, there appears to be a selective packaging of different molecular forms of AChE into the regulated versus the constitutive secretory pathway. Both the specificity of sorting of AChE and the regulation of its secretion suggest that AChE may play a more dynamic role in synaptic function than has been recognized previously.

Acetylcholinesterase↗
PubMed1994

Effects of anisosmotic conditions on the cytoskeletal architecture of cultured PC12 cells.

PC12 cells show a classical volume regulatory process when submitted to hypo-osmotic conditions. The present study examined the effects of such osmotic shock on the structural organization of different cytoskeletal elements. Results were obtained by use of different light and electron microscopy techniques combined with immunostaining methods. It appeared that the osmotically induced changes in cell volume were concomitant with important modifications in the organization of the microfilament network. Microfilaments concentrated in the perinuclear area, leaving only radial extensions of poorly organized structures in the cytoplasm. The latter were the only actin structures immunologically stained in the cytoplasm and seemed to anchor to the plasma membrane. Measurements of the fluorescence intensity of PC12 cells treated with FITC-labeled phalloidin indicated a progressive depolymerization, followed by a repolymerization of F-actin. This occurs in parallel with microfilament reorganization and volume regulatory processes. The appearance of microfilament reorganization was a function of both the incubation period and the amplitude of the osmolarity changes. During the first minutes of osmotic shock, a decrease was observed in the density and length of microvilli, which normally cover the PC12 cell surfaces, suggesting an early reorganization of the underlying microfilament network. Microtubules and intermediate filament networks were not affected by the hypo-osmotic conditions.

Actin Cytoskeleton↗
PubMed1990

Differential effects of NGF, FGF, EGF, cAMP, and dexamethasone on neurite outgrowth and sodium channel expression in PC12 cells.

PC12 cells are a pheochromocytoma cell line that can be made to differentiate into sympatheticlike neurons by nerve growth factor (NGF). An essential component of the NGF-induced differentiation is the development of action potentials and sodium channels. Using whole-cell clamp we have confirmed that NGF produces a 5- to 6-fold increase in sodium channel density. The sodium channels induced by NGF are not different from those in cells not treated with NGF and are similar to those in other cell types. Basic fibroblast growth factor (FGF), another growth factor that causes PC12 cells to differentiate into sympathetic-like neurons, also produces a 5- to 6-fold increase in sodium current density with channels indistinguishable from those in PC12 cells treated and not treated with NGF. Basic FGF produces the same or somewhat larger increase in sodium channel density but much less neurite outgrowth. In contrast, epidermal growth factor does not produce neurite outgrowth but induces a small, reproducible increase in sodium channel density. Cyclic AMP produces spike-like processes but not neurites and results in a decrease in sodium current and sodium current density. Dexamethasone, a synthetic glucocorticoid, inhibits the increase in sodium current and sodium current density but does not antagonize the neurite outgrowth induced by NGF. Thus, although the increase in sodium channel expression induced by NGF and basic FGF parallels the changes in morphology that lead to neurite outgrowth, it clearly does not depend on them. The results show that different aspects of neuronal differentiation might be independently regulated by the microenvironment.

Adrenal Gland Neoplasms↗
PubMed1995

Nerve growth factor regulates transforming growth factor-beta 1 gene expression by both transcriptional and posttranscriptional mechanisms in PC12 cells.

PC12 cells express two transforming growth factor (TGF)-beta 1 transcripts, 1.7 and 2.5 kb in size. Other TGF-beta s are expressed at much lower levels. Incubation with nerve growth factor (NGF) produced a time- and dose-dependent increase in content of TGF-beta 1 transcripts. The level of the smaller mRNA increased little, whereas that of the 2.5-kb transcript increased more, with the latter becoming the predominant TGF-beta 1 message. NGF differentially regulated the stability of both mRNAs. The half-life of the 2.5-kb transcript was not altered by NGF; however, the half-life of the 1.7-kb mRNA was approximately 6 h and increased to > 30 h on incubation with NGF. In addition, induction of the 2.5-kb TGF-beta 1 mRNA by NGF required de novo protein synthesis, whereas induction of the 1.7-kb TGF-beta 1 mRNA was independent of protein synthesis. The NGF effect was independent of protein kinase C activation, which also preferentially induced the larger transcript. PC12 cells release a significant amount of TGF-beta 1, and incubation with NGF further increases TGF-beta 1 production. This factor is released in a latent form. These results indicate that an increase in expression and secretion of TGF-beta 1 accompanies neuronal differentiation in PC12 cells. Regulation of TGF-beta 1 gene expression by NGF is complex, involving both increased transcription of the TGF-beta 1 gene and stabilization of the smaller TGF-beta 1 transcript.

Animals↗
PubMed1992

Characterization of ATP receptor which mediates norepinephrine release in PC12 cells.

PC12 cells, a rat pheochromocytoma cell line, has been reported to release norepinephrine in response to extracellular ATP in the presence of extracellular Ca2+. The potency order of ATP analogues was adenosine 5'-O-(3-thiotriphosphate) greater than ATP greater than adenosine 5'-O-(1-thiotriphosphate) = 2-methylthioadenosine 5'-triphosphate (MeSATP) greater than 2'- and 3'-O-(4-benzoyl-benzoyl)ATP (BzATP) greater than ADP greater than 5-adenylylimidodiphosphate. Adenosine 5'-O-(2-thiodiphosphate), beta, gamma-methyleneadenosine 5'-triphosphate, AMP and adenosine were inactive. The ATP action in the absence of extracellular Ca2+, suggests a small but appreciable contribution of intracellular Ca2+ mobilization, for norepinephrine release. However, for some ATP derivatives, like BzATP, almost no contribution of the phospholipase C-Ca2+ pathway is suggested, based on their low activity in inositol phosphates production. To identify the ATP-receptor protein, PC12 cell membranes were photoaffinity-labeled with [32P]BzATP. SDS-PAGE analysis showed that a 53-kDa protein labeling was inhibited by ATP and its derivatives, as well as by P2-antagonists, suramin and reactive blue 2, which inhibit the nucleotide-induced norepinephrine release. The inhibitory activity of the nucleotides was, in parallel with their potency, to induce norepinephrine release. Despite their inability to release norepinephrine, GTP and GTP gamma S inhibited the BzATP labeling, suggesting the participation of a putative G protein in the ATP-receptor-mediated actions. We suggest that the 53-kDa protein on the PC12 cell surface is an ATP receptor, which mediates the norepinephrine release, depending, mainly, on extracellular Ca2+ gating.

Adenosine Triphosphate↗
PubMed1989

Nerve growth factor-induced decrease in the calpain activity of PC12 cells.

PC12 cells are a nerve growth factor-responsive clone derived from a rat pheochromocytoma. Treatment with nerve growth factor causes the cells to differentiate. One of the hallmarks of this differentiation is the generation of neurites. PC12 cells contain both calpain I and calpain II; about 90% of the total calpain activity is due to calpain II. Treatment of the cells with nerve growth factor causes a time-dependent decrease in calpain activity, more than 50% being lost over a 5-day period. Both the decrease in calpain activity and the growth of neurites are reversible upon the removal of nerve growth factor from the cultures. Agents other than nerve growth factor that cause neurite outgrowth, such as fibroblast growth factor and dibutyryl cyclic AMP, also cause a decrease in calpain activity. Calpain levels, as detected with immunoblotting or immunohistochemistry, show no decrease. Removal of calpastatin, the endogenous inhibitor of the calpains, by phenyl-Sepharose chromatography increases the calpain activity of extracts from both control and nerve growth factor-treated cells and brings the activity in the extracts from treated cells up to the activity in those from controls. Calpastatin-containing fractions from extracts of nerve growth factor-treated cells inhibit more calpain activity than do comparable fractions from control cells. These studies suggest that nerve growth factor causes a decrease in the activity of calpain in morphologically differentiating PC12 cells by causing an increase in the activity of calpastatin.

Adrenal Gland Neoplasms↗
PubMed1996

Functional characterization of adenosine A2 receptors in Jurkat cells and PC12 cells using adenosine receptor agonists.

The effect of several adenosine analogues on cyclic AMP accumulation was examined in the rat phaeochromocytoma cell PC12 and in the human T-cell leukaemia cell Jurkat, selected as prototypes of cells predominantly expressing adenosine A2A or A2B receptors. Using the reverse transcription-polymerase chain reaction it was, however, demonstrated that the Jurkat cell and the PC12 cell express both A2A and A2B receptor mRNA, albeit in different relative proportions. In PC12 cells the concentration required for half-maximal response (EC50) for the full agonist 5'-N-ethyl-carboxamidoadenosine (NECA) was 30 times lower than in Jurkat cells. There was no significant difference in the pA2 for the antagonist 5-amino-9-chloro-2-(2-furanyl)- 1,2,4-triazolo(1,5-C)quinazolinemonomethanesulphonate (CGS 15943) between the two cell types. In the presence of forskolin (1 microM in PC12 cells; 10 microM in Jurkat cells) the EC50 value for NECA was reduced two-to sixfold. Forskolin also increased the maximal cAMP accumulation twofold in PC12 cells and sevenfold in Jurkat cells. A series of 2-substituted adenosine analogues CV 1808 (2-phenylamino adenosine), CV 1674 [2-(4-methoxyphenyl)adenosine], CGS 21680 ¿2-[p-(2-carbonylethyl)phenylethylamino]-5'-N-ethyl- carboxamido adenosine¿, and four 2-substituted isoguanosines, SHA 40 [2-(2-phenylethoxy)adenosine; PEA], SHA 91 [2-(2-cyclohexylethoxy)adenosine; CEA], SHA 118 ¿2-[2-(p-methylphenyl)ethoxy]adenosine; MPEA¿, and SHA 125 (2-hexyloxyadenosine; HOA), all raised cAMP accumulation in PC12 cells, but had minimal or no effect in Jurkat cells. In the PC12 cells the addition of forskolin (1 microM) reduced the EC50 by a factor of 2(CV 1808) to 12 (SHA 125). In Jurkat cells all the analogues gave a significant, but submaximal, cAMP response in the presence of forskolin (10 microM), but they were essentially inactive in its absence. The results show that a series of 2-substituted adenosine analogues can be used to discriminate between A2A and A2B receptors. The two receptor subtypes appear to coexist, even in clonal cells selected for typical pharmacology. A2 receptor pharmacology can therefore be complex.

Adenosine↗