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PubMed2000

Catecholamines inhibit microglial nitric oxide production.

Viral infection in the central nervous system can induce nitric oxide production, which serves as a major host defense against viral infection. Under stress, catecholamine secretion is enhanced and immune responses are diminished in animals. Using N9 microglial cells, this study tested the effect of catecholamines on microglial nitric oxide production. Results indicated that each member of the catecholamine family (dopamine, norepinephrine and epinephrine) was a potent inhibitor of the microglial nitric oxide production. In contrast, dopa, the immediate precursor of the catecholamine biosynthesis pathway, was a weak inhibitor, except at very high concentrations. The inhibitory effect of catecholamines was mimicked by an alpha-adrenergic receptor agonist (phenylephrine) and by a beta-adrenergic receptor agonist (isoproterenol), but not by forskolin or analogs of cyclic adenosine monophosphate. Western blot analysis indicated that catecholamines caused a slight decrease in the formation of inducible nitric oxide synthase. These results suggest that catecholamines have the ability to block nitric oxide production by microglia, which could partially explain the impaired immune protection against viral infection in the central nervous system in stressed animals.

Adrenergic Agonists↗
PubMed1979

Estimation of catecholamines in human plasma by ion-exchange chromatography coupled with fluorimetry.

Estimation of catecholamines in human plasma was made by ion-exchange chromatography coupled with fluorimetry. Catecholamines in deproteinized plasma were adsorbed onto Amberlite CG-50 (pH 6.5, buffered with 0.4 M phosphate buffer) and selectively eluted by 0.66 M boric acid. The catecholamine fraction was separated further on a column of Amberlite IRC-50 which was coupled with a device for the automated performance of the trihydroxyindole method (epinephrine and norepinephrine) or the 4-aminobenzoic acid-oxidation method (dopamine). One sample could be analysed within 25 min with either method. The lower detection limits were 0.02 ng for epinephrine and dopamine, and 0.04 ng for norepinephrine. Plasma catecholamine contents of healthy adults at rest were epinephrine 0.07 +/- 0.01 ng/ml (n = 19), norepinephrine 0.27 +/- 0.03 ng/ml (n = 19) and dopamine 0.22 +/- 0.03 ng/ml (n = 26). The procedure of adsorption and elution of the plasma catecholamines by ion-exchange resin was simple, the simplicity contributing to constant recovery. The catecholamine fraction could be analysed without evaporation of the eluate. The analytical column could be used for the analysis of more than 1000 samples before excessive back-pressure developed. Our method of continuous measurement of plasma catecholamine fulfils clinical requirements.

Catecholamines↗
PubMed2004

Tetrapeptides on N- and C-terminal regions of mastoparan inhibit catecholamine release from chromaffin cells by blocking nicotinic acetylcholine receptor.

Mastoparan (MP), a tetradecapeptide in wasp venom, has been reported to evoke catecholamine release, but also reported to inhibit secretory response upon nicotinic stimulation in adrenal chromaffin cells. To elucidate the inhibitory mechanism of MP, we examined the effect of two MP fragments (INLK-NH2 and KKIL-NH2) on catecholamine release in bovine adrenal chromaffin cells. These MP fragments inhibited catecholamine release induced by nicotinic stimulation in a noncompetitive manner. These fragments did not affect catecholamine release evoked by high [K+] or by other secretagogues, neither caused catecholamine release by themselves. Replacement by hydrophobic and basic amino acids of the MP fragments enhanced the inhibitory effects on ACh-evoked catecholamine release. Among 23 analogs of the MP fragments, (Nle)3-R-NH2 showed the most potent inhibition with IC50 = 541 microM. These results suggested that the MP fragments selectively inhibit the secretory response to nicotinic stimulation by attacking nAChR on the site(s) made up of hydrophobic and acidic amino acids but other than ACh-binding sites. This mechanism may explain the inhibitory action of MP on nicotine-evoked catecholamine release.

Adrenal Medulla↗
PubMed1971

The effect of salts on catecholamine fluxes and adenosine triphosphatase activity in storage vesicles from the adrenal medulla.

1. Influx and efflux of catecholamine and adenosine triphosphatase activity in storage vesicles from the adrenal medulla were studied with dl-[(14)C]adrenaline in different media. 2. The lowest values for flux and adenosine triphosphatase activity were observed in sucrose media in which an ATP-dependent influx of catecholamine compensated for an efflux of the same magnitude. Efflux in the presence or absence of ATP was similar. 3. In media containing sodium succinate or glutarate adenosine triphosphatase activity was higher and the ATP-dependent influx of catecholamine was about twice that observed in iso-osmotic sucrose medium. In the presence of ATP influx and efflux of catecholamine were balanced; in its absence there was a net release of catecholamine, since efflux was more than twice the influx. Efflux in the presence or absence of ATP was similar. 4. In media containing sodium or potassium chloride and in the presence of ATP influx and adenosine triphosphatase activity were further enhanced, but in the absence of ATP there was no further increase in influx, since catecholamine was released with or without ATP at the same rate. Efflux was therefore twice as high in the presence of ATP as in its absence. 5. Sodium nitrate suppressed the ATP-dependent influx nearly completely, but caused a greatly enhanced efflux, which was twice as high in the presence of ATP as in its absence. 6. The extinction of vesicular suspensions remained unchanged in the presence of ATP under conditions where the catecholamine efflux was balanced by the influx. Under conditions where the efflux was not compensated by influx, the extinction of the suspensions decreased in the presence of ATP more than in its absence.

Adenosine Triphosphatases↗
PubMed1994

Platelet catecholamine concentrations after short-term stress in normal subjects.

1. Four studies were designed to test the hypothesis that platelet catecholamine levels may provide a stable index of circulating plasma catecholamine concentrations, and that these are unaffected by acute elevations of plasma levels with physical and psychological stress. 2. To assess the biological variability within individuals, ten subjects were sampled on five occasions over 8-30 h. The intra-individual coefficients of variation for plasma and platelet noradrenaline levels were 19.5 +/- 10% and 9.5 +/- 4.2%, respectively, and for plasma and platelet adrenaline levels 48.3 +/- 22% and 25.3 +/- 8.4%, respectively. 3. Three other studies investigating the response to physical and psychological stress were performed. In the first study, plasma and platelet catecholamine levels were studied in 12 healthy subjects before and after bicycle ergometry. Plasma catecholamine concentrations increased [noradrenaline by +346 +/- 323% (P = 0.002) and adrenaline by +314 +/- 352% (P = 0.003)], whereas platelet concentrations showed little change [noradrenaline +4 +/- 18% (P = 0.94) and adrenaline +38 +/- 116% (P = 0.67)]. 4. In the study, catecholamine concentrations were measured in eight subjects after hand immersion in iced water. Plasma noradrenaline concentrations increased significantly (+58 +/- 19%, P = 0.001), but no significant change was found in plasma adrenaline concentrations (+8 +/- 44%, P = 0.48). Platelet catecholamine concentrations showed no significant change (noradrenaline +15 +/- 15%, P = 0.052, and adrenaline 19 +/- 82%, P = 0.84). 5. In the third study, catecholamine concentrations were measured in 22 medical students before and after their end-of-year examination.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1996

Role of catecholamines in platelet function: pathophysiological and clinical significance.

Platelets are involved in the pathogenesis of vascular damage in both atherosclerosis and arterial hypertension. Their reactivity in vivo is influenced by different factors, including sympathoadrenal activation, plasma levels of atherogenic lipoproteins and haemorrheological changes. In the present review, we examine the modulation of platelet function by the sympathoadrenal system and concentrate on the role of circulating catecholamines in the control of platelet responses. Human platelets exhibit both adrenergic and dopaminergic receptors that are influenced by different catecholamines. alpha(2)-Adrenoceptors of alpha(2A) subtype prevail on platelet membrane; through their stimulation, catecholamines potentiate the effects of other agonists and, at higher concentrations, initiate platelet responses, including aggregation, secretion and arachidonate pathway activation. Physiological and pathological conditions causing sympathoadrenal activation in vivo, i.e. physical activity, mental stress, insulin-induced hypoglycaemia, acute coronary ischaemia and heart failure, modify the circulating platelet populations and modulate platelet reactivity through an increase in circulating catecholamines. A sympathoadrenal hyperactivation modifies the function of circulating platelets through direct catecholamine effects, catecholamine-induced changes of haemodynamic factors and lipid pattern and inhibition of the vascular eicosanoid synthesis. The catecholamine effects on platelet function can be involved in the interplay among stress, adrenomedullary system activation and cardiovascular diseases.

Adrenal Glands↗
PubMed1994

Influence of the CNS environment on chromaffin cell survival and catecholamine secretion patterns.

Chromaffin cells implanted into the CNS have been used as a potential source of sustained catecholamine delivery, although their survival and continued catecholamine secretion are controversial. In addition, chromaffin cells exhibit a high degree of neurochemical plasticity in response to environmental factors. The present aims were to determine whether the CNS provides a supportive environment for sustained catecholamine production in transplanted chromaffin cells and to assess whether this novel environment alters patterns of catecholamine secretion. Catecholamine release from bovine chromaffin cells implanted into the rat midbrain was determined in brain slices. In addition, alterations in catecholamine secretion patterns, particularly adrenaline/noradrenaline ratios, were compared in vitro versus in transplants. Results indicated that brain slices containing chromaffin cell implants released high basal and nicotine-stimulated levels of adrenaline and noradrenaline. It is surprising that although adrenaline/noradrenaline ratios steadily declined in culture, this did not occur when cells were transplanted to the CNS in the early postharvesting phases. However, if cells were transplanted following longer periods in culture, adrenaline/noradrenaline ratios remained low. Together, these results suggest that the CNS can provide a supportive environment for chromaffin cell survival and that the pattern of catecholamine secretion can be optimized by prior in vitro manipulation.

Adrenal Glands↗
PubMed2001

Stimulation of catecholamine synthesis in cultured bovine adrenal medullary cells by leptin.

Recently, we characterized leptin receptors in bovine adrenal medullary cells (Yanagihara et al. 2000). Here we report the stimulatory effect of leptin on catecholamine synthesis in the cells. Incubating cells with leptin (10 nM) for 20 min increased the synthesis of 14C-catecholamines from [14C]tyrosine, but not from L-3,4-dihydroxyphenyl [3-14C]alanine. The stimulation of catecholamine synthesis in the cells by leptin was associated with the phosphorylation and activation of tyrosine hydroxylase, the rate-limiting enzyme of catecholamine biosynthesis. The incubation of cells with leptin resulted in a rapid activation of the mitogen-activated protein kinases (MAPKs). An inhibitor of MAPK kinase, U0126, nullified the stimulatory effect of leptin on the synthesis of 14C-catecholamines. Leptin potentiated the stimulatory effect of acetylcholine on 14C-catecholamine synthesis, whereas leptin failed to enhance the phosphorylation and activation of tyrosine hydroxylase induced by acetylcholine. These findings suggest that leptin stimulates catecholamine synthesis via the activation of tyrosine hydroxylase by two different mechanisms, i.e., one is dependent on tyrosine hydroxylase phosphorylation mediated through the MAPK pathway and the second is independent of enzyme phosphorylation.

Acetylcholine↗
PubMed2001

Catecholamine release and uptake in the mouse prefrontal cortex.

Monitoring the release and uptake of catecholamines from terminals in weakly innervated brain regions is an important step in understanding their importance in normal brain function. To that end, we have labeled brain slices from transgenic mice that synthesize placental alkaline phosphatase (PLAP) on neurons containing tyrosine hydroxylase with antibody-fluorochrome conjugate, PLAP-Cy5. Excitation of the fluorochrome enables catecholamine neurons to be visualized in living tissue. Immunohistochemical fluorescence with antibodies to tyrosine hydroxylase and dopamine beta-hydroxylase revealed that the PLAP labeling was specific to catecholamine neurons. In the prefrontal cortex (PFC), immunohistochemical fluorescence of the PLAP along with staining for dopamine transporter (DAT) and norepinephrine transporter (NET) revealed that all three exhibit remarkable spatial overlap. Fluorescence from the PLAP antibody was used to position carbon-fiber microelectrodes adjacent to catecholamine neurons in the PFC. Following incubation with L-DOPA, catecholamine release and subsequent uptake was measured and the effect of uptake inhibitors examined. Release and uptake in NET and DAT knockout mice were also monitored. Uptake rates in the cingulate and prelimbic cortex are so slow that catecholamines can exist in the extracellular fluid for sufficient time to travel approximately 100 microm. The results support heterologous uptake of catecholamines and volume transmission in the PFC of mice.

Alkaline Phosphatase↗
PubMed2002

The mechanism of glucose-induced catecholamine stimulation.

Catecholamines are important hormones for maintaining homeostasis and may be secreted in response to several different stimuli. A report by Robertson and Porte in 1974 made the unexpected observation that acute administration of hypertonic glucose stimulates catecholamine secretion. Our study reassessed this observation by measuring individual catecholamines, explored its potential mechanism, and quantitated it relative to exercise and hypoglycemia-stimulated catecholamine secretion. We hypothesized that the mechanism of glucose-induced catecholamine secretion was related to an acute increase in plasma osmolality, which we tested with the nonmetabolizable hexose mannitol. In 56 studies, 14 normal adults underwent 4 partially randomized studies. The 4 study conditions consisted of the following: (1) rapid intravenous injection of 20 g of glucose; (2) rapid intravenous injection of 20 g of mannitol; (3) acute exercise (80 J/kg); and (4) insulin-induced hypoglycemia. Our results demonstrate that a significant increase in plasma catecholamine concentration occurs following each of the above stimuli, but its composition differs relative to the magnitude of epinephrine versus norepinephrine secretion. We conclude that the mechanism of glucose-induced catecholamine stimulation is the acute elevation in plasma osmolality induced by glucose, and that its stimulation is less than that which occurs following exercise for norepinephrine and less than that which occurs following hypoglycemia for epinephrine.

Adult↗
PubMed1995

Enhanced cAMP production mediates the stimulatory action of pituitary adenylate cyclase activating polypeptide (PACAP) on in vitro catecholamine secretion from bovine adrenal chromaffin cells.

The 38 amino acid peptide pituitary adenylate cyclase activating polypeptide (PACAP) induced a dose dependent increase of catecholamine secretion in cultures of bovine chromaffin cells. This secretagogue activity of PACAP was strictly dependent on the presence of calcium in the culture medium. If calcium was omitted from the medium no effect of PACAP on catecholamine secretion could be detected during an incubation of 20 min. Preincubation of cells with 1 nM PACAP for 5 min facilitated the subsequent nicotine stimulated catecholamine secretion during a 20 min incubation without addition of the peptide. PACAP induced catecholamine secretion was clearly accompanied by a dose dependent increase of intracellular cAMP concentrations. The percentage of cells responding to PACAP with increased catecholamine secretion was assessed by immunocytochemistry of the transient appearance of dopamine-beta-hydroxylase, associated with the membranes of the chromaffin granules on the cell surface during the secretory process. About 70% of adrenal medullary cells responded to 100 nM PACAP with enhanced secretory activity. Though PACAP stimulated catecholamine secretion, we did not observed major effects on intracellular free calcium concentrations ([Ca2+]i) as determined with fura-2 by single cell fluorescence microscopy. In maximally 20% of the cells a rise in [Ca2+]i in response to a challenge with 500 nM PACAP was observed. Lower concentrations of PACAP were without an effect on [Ca2+]i. These data indicate that the stimulatory action of PACAP on in vitro catecholamine secretion from bovine chromaffin cells is linked to a rise of intracellular cAMP.

Adrenal Medulla↗
PubMed1997

Tissue plasminogen activator (t-PA) is targeted to the regulated secretory pathway. Catecholamine storage vesicles as a reservoir for the rapid release of t-PA.

Tissue-type plasminogen activator (t-PA) is a serine protease that plays a central role in the regulation of intravascular thrombolysis. The acute release of t-PA in vivo is induced by a variety of stimuli including exercise, trauma, and neural stimulation. These types of stimuli also result in sympathoadrenal activation and exocytotic release of amines and proteins from catecholamine storage vesicles of the adrenal medulla and sympathetic neurons. Therefore, we tested the hypothesis that t-PA is packaged in and released directly from catecholamine storage vesicles, using several chromaffin cell sources including the rat pheochromocytoma PC-12 chromaffin cell line, primary cultures of bovine adrenal chromaffin cells, and human pheochromocytoma. t-PA was expressed in chromaffin cells as detected by Northern blotting, immunoprecipitation of [35S]Met-labeled t-PA, and specific t-PA enzyme-linked immunosorbent assay of cell homogenates. In addition, chromaffin cell t-PA was enzymatically active by fibrin zymography. To explore the subcellular localization of the expressed t-PA, PC-12 cells were labeled with [3H]norepinephrine, homogenized, and subjected to sucrose density fractionation. [3H]Norepinephrine and t-PA antigen were co-localized to the same subcellular fraction with a major peak at 1.4 M sucrose, consistent with the buoyant density of catecholamine storage vesicles. In addition, catecholamine storage vesicle lysates isolated from human pheochromocytoma tumors were enriched approximately 30-fold in t-PA antigen, compared with tumor homogenate. Furthermore, exposure of PC-12 cells or primary bovine adrenal chromaffin cells to chromaffin cell secretagogues (60 microM nicotine, 55 mM KCl, or 2 mM BaCl2) resulted in co-release of t-PA in parallel with catecholamines. These data demonstrate that t-PA is expressed in chromaffin cells, is sorted into the regulated pathway of secretion, and is co-released with catecholamines by chromaffin cell stimulation. Catecholamine storage vesicles may be an important reservoir and sympathoadrenal activation an important physiologic mechanism for the rapid release of t-PA. In addition, expression of t-PA by chromaffin cells suggests a role for this protease in the proteolytic processing of chromaffin cell proteins.

Animals↗
PubMed2001

Proteolytic cleavage of chromogranin A (CgA) by plasmin. Selective liberation of a specific bioactive CgA fragment that regulates catecholamine release.

Chromogranin A (CgA), the major soluble protein in catecholamine storage vesicles, serves as a prohormone that is cleaved into bioactive peptides that inhibit catecholamine release, providing an autocrine, negative feedback mechanism for regulating catecholamine responses during stress. However, the proteases responsible for the processing of CgA and release of bioactive peptides have not been established. Recently, we found that chromaffin cells express components of the plasmin(ogen) system, including tissue plasminogen activator, which is targeted to catecholamine storage vesicles and released with CgA and catecholamines in response to sympathoadrenal stimulation, and high affinity cell surface receptors for plasminogen, to promote plasminogen activation at the cell surface. In the present study, we investigated processing of CgA by plasmin and sought to identify specific bioactive CgA peptides produced by plasmin proteolysis. Highly purified human CgA (hCgA) was produced by expression in Escherichia coli and purification using metal affinity chromatography. hCgA was digested with plasmin. Matrix-assisted laser desorption/ionization mass spectrometry identified a major peptide produced with a mass/charge ratio (m/z) of 1546, corresponding uniquely to hCgA-(360-373), the identity of which was confirmed by reverse phase high pressure liquid chromatography and amino-terminal microsequencing. hCgA-(360-373) was selectively liberated by plasmin from hCgA at early time points and was stable even after prolonged exposure to plasmin. The corresponding synthetic peptide markedly inhibited nicotine-induced catecholamine release from pheochromocytoma cells. These results identify plasmin as a protease, present in the local environment of the chromaffin cell, that selectively cleaves CgA to generate a bioactive fragment, hCgA-(360-373), that inhibits nicotinic-mediated catecholamine release. These results suggest that the plasminogen/plasmin system through its interaction with CgA may play a major role in catecholaminergic function and suggest a specific mechanism as well as a discrete CgA peptide through which this effect is mediated.

Amino Acid Sequence↗
PubMed1973

Primary cultures of dissociated sympathetic neurons. II. Initial studies on catecholamine metabolism.

Initial studies are reported on the catecholamine metabolism of low-density cultures of dissociated primary sympathetic neurons. Radioactive tyrosine was used to study the synthesis and breakdown of catecholamines in the cultures. The dependence of catecholamine synthesis and accumulation on external tyrosine concentration was examined and a concentration which is near saturation, 30 microM, was chosen for further studies. The free tyrosine pool in the nerve cells equilibrated with extracellular tyrosine within 1 h; the total accumulation of tyrosine (free tyrosine plus protein, catecholamines, and metabolites) was linear for more than 24 h of incubation. Addition of biopterin, the cofactor of tyrosine hydroxylase, only slightly enhanced catecholamine biosynthesis by the cultured neurons. However, addition of reduced ascorbic acid, the cosubstrate for dopamine beta-hydroxylase, markedly stimulated the conversion of dopamine (DA) to norepinephrine (NE). Phenylalanine, like tyrosine, served as a precursor for some of the DA and NE produced by the cultures, but tyrosine always accounted for more than 90% of the catecholamines produced. The DA pool labeled rapidly to a saturation level characteristic of the age of the culture. The NE pool filled more slowly and was much larger than the DA pool. The disappearance of radioactive NE and DA during chase experiments followed a simple exponential curve. Older cultures showed both more rapid production and more rapid turnover of the catecholamines than did younger cultures, suggesting a process of maturation.

Animals↗
PubMed1976

Catecholamine metabolism in neuroblastoma.

Previous studies indicating the importance of catecholamine metabolism in neuroblastoma were briefly reviewed. Metabolic pathways were presented showing how the major urinary metabolites 3-methoxy-4-hydroxymandelic acid (VMA) and 3-methoxy-4-hydroxy-phenylacetic acid (HVA) are formed from norepinephrine and from dopamine plus 3,4-dihydroxyphenylalanine (DOPA), respectively. For 289 neuroblastoma patients at the time of diagnosis, the urinary excretion of VMA was significantly elevated in 75%, and HVA was elevated in 80%. Periodic assay of these metabolites during the course of the disease revealed that the excretion trends were of prognostic value with 80-90% reliability. By contrast, when the excretion in only the initial urine specimens was considered, the survival rate was the same for patients with normal, and with significantly elevated, excretion. Review of the results of tracer studies aimed at elucidating the in vivo metabolic origins of the urinary metabolites suggested that a) in neuroblastoma, the catecholamines were largely inactivated by intracellular metabolism in the tumor cells; b) there was excess production and excretion of the norepinephrine precursors, DOPA and dopamine; and c) in the tumors of most neuroblastoma patients, the initial enzyme in catecholamine synthesis, tyrosine hydroxylase, had an activity comparable with that in normal adrenal glands. The importance of the metabolism of catecholamines in patients with neuroblastoma was stressed: a) The excretion of elevated levels of urinary catecholamine metabolites were useful in diagnosis and in following the course of the disease, and b) study of the catecholamine metabolism in these patients permitted examination of possible relationships between the activity of the enzymes involved in catecholamine synthesis and the malignancy of this tumor.

Catecholamines↗
PubMed1989

Catecholamine effects on testicular testosterone production in the gonadally active and the gonadally regressed adult golden hamster.

Several lines of evidence support a role of testicular innervation and peripheral catecholamines in the control of male gonadal function, particularly before puberty. It was therefore of interest to compare the effects of catecholamines on androgen production during the periods of gonadal activity and quiescence in a seasonally breeding species. We have examined direct effects of epinephrine (EPI), norepinephrine (NE), the beta-adrenergic agonist isoproterenol (ISO), and the alpha-adrenergic agonist phenylephrine (PHE) on testicular testosterone (T) production in hamsters with gonadal regression induced by 12 wk exposure to short photoperiod (SD) and in gonadally active hamsters maintained in long photoperiod (LD). Fragments of decapsulated testes were incubated with various combinations of these catecholamines (10(-5)-10(-9) M), human chorionic gonadotropin (hCG; 3.1 mIU/ml), the beta-receptor antagonist propranolol (10(-5) M) and the alpha-l-receptor antagonist prazosin (10(-5) M), for 6 h. In the incubations of testes from LD hamsters, the accumulation of T in the medium was stimulated by hCG but not affected by either catecholamine. However, EPI, NE, and PHE at 10(-5) M, but not ISO, augmented the stimulation of T by hCG. In sharp contrast to these findings, T production by the regressed testes of SD animals was stimulated by EPI (at 10(-8)-10(-5) M), NE (at 10(-6)-10(-5) M), and PHE (at 10(-6)-10(-5) M) in a dose-related manner, but unaffected by ISO. These stimulatory effects were prevented by prazosin, but not by propranolol. Moreover, 10(-5) M of EPI, NE, and PHE augmented the stimulatory effect of hCG on T production. We conclude that the seasonal transition from gonadal activity to quiescence in the adult golden hamster is accompanied by a major increase in the responsiveness of testicular steroidogenesis to catecholamines acting via the alpha-1-adrenoreceptor and that catecholamines can modulate Leydig cell response to gonadotropins in this species. These findings could be related to up-regulation of the alpha-1-receptor in the testis of the SD animal and suggest that catecholamines may be involved in the regulation of the testis during physiological suppression of gonadotropin release and during stress.

Animals↗
PubMed2000

Catecholamines up-regulate lipopolysaccharide-induced IL-6 production in human microvascular endothelial cells.

The catecholamine-mediated modulation of the cytokine network has primarily been demonstrated for leukocytes. Whereas catecholamines decrease the LPS-induced production of IL-6 by leukocytes, serum levels of IL-6 are dramatically increased by the catecholamine epinephrine in animal endotoxemia models. We now demonstrate that epinephrine as well as norepinephrine can induce IL-6 in an endothelial cell line (HMEC-1). Furthermore, these catecholamines could even potentiate the LPS-induced IL-6 protein production. The synergistic effect of catecholamines and LPS could be reproduced in primary human skin microvascular endothelial cells. The catecholamine-induced IL-6 stimulation is based on increased IL-6 mRNA levels. RNA stability assays revealed that this regulation is not a result of enhanced RNA stability and therefore is most likely due to an increased transcription. Treatment with cycloheximide indicated that new protein synthesis is not necessary for this transcriptional up-regulation of IL-6 mRNA. Preincubation with alpha and beta receptor antagonists showed that the effect is mediated by beta(1)- and beta(2)-adrenergic receptors. Thus, endothelial cells might be a possible source of increased IL-6 production observed in situations such as stress or septic shock, in which catecholamines are elevated due to endogenous production or exogenous application.

Adrenergic beta-Antagonists↗
PubMed1980

Effects of cyclopropane on catecholamine release from bovine adrenal medulla.

The direct effects of cyclopropane on both adrenal medullary release of catecholamines and release of catecholamines from isolated chromaffin granules were examined. Cyclopropane had no effect on the spontaneous release of catecholamines from perfused bovine adrenals, while it reversibly inhibited carbachol-induced release of catecholamines in a dose-dependent manner. At 20 per cent cyclopropane, catecholamine release was reduced to 52 per cent of control. Cyclopropane exerted no action on spontaneous release or Mg++-ATP-dependent release of catecholamines from isolated chromaffin granules. Thus, the authors conclude that the direct action of cyclopropane on the adrenal medullary release of catecholamines is inhibitory, and that chromaffin granules are not the site of action of this anesthetic.

Adenosine Triphosphate↗