scholarly journals Gene expression and function of adenosine A2A receptor in the rat carotid body

2000 ◽  
Vol 279 (2) ◽  
pp. L273-L282 ◽  
Author(s):  
Shuichi Kobayashi ◽  
Laura Conforti ◽  
David E. Millhorn
Keyword(s):  
Carotid Body ◽  
Cellular Response ◽  
Cell Voltage ◽  
Type I ◽  
Type I Cells ◽  
Carotid Bodies ◽  
Intracellular Ca ◽  
Immunohistochemical Studies ◽  
I Cells ◽  
Receptor Mrnas

The present study was undertaken to determine whether rat carotid bodies express adenosine (Ado) A2A receptors and whether this receptor is involved in the cellular response to hypoxia. Our results demonstrate that rat carotid bodies express the A2A and A2B Ado receptor mRNAs but not the A1 or A3 receptor mRNAs as determined by reverse transcriptase-polymerase chain reaction. In situ hybridization confirmed the expression of the A2A receptor mRNA. Immunohistochemical studies further showed that the A2A receptor is expressed in the carotid body and that it is colocalized with tyrosine hydroxylase in type I cells. Whole cell voltage-clamp studies using isolated type I cells showed that Ado inhibited the voltage-dependent Ca2+ currents and that this inhibition was abolished by the selective A2A receptor antagonist ZM-241385. Ca2+ imaging studies using fura 2 revealed that exposure to severe hypoxia induced elevation of intracellular Ca2+ concentration ([Ca2+]i) in type I cells and that extracellularly applied Ado significantly attenuated the hypoxia-induced elevation of [Ca2+]i. Taken together, our findings indicate that A2A receptors are present in type I cells and that activation of A2Areceptors modulates Ca2+ accumulation during hypoxia. This mechanism may play a role in regulating intracellular Ca2+homeostasis and cellular excitability during hypoxia.

Interactions between hypoxia and hypercapnic acidosis on calcium signaling in carotid body type I cells

2000 ◽  
Vol 279 (1) ◽  
pp. L36-L42 ◽  
Author(s):  
Leonardo L. T. Dasso ◽  
Keith J. Buckler ◽  
Richard D. Vaughan-Jones
Keyword(s):  
Carotid Body ◽  
Neonatal Rat ◽  
Single Type ◽  
Type I ◽  
Hypercapnic Acidosis ◽  
Body Type ◽  
Type I Cells ◽  
Carotid Bodies ◽  
Intracellular Ca ◽  
I Cells

The effects of hypercapnic acidosis and hypoxia on intracellular Ca2+concentration ([Ca2+]i) were determined with Indo 1 in enzymatically isolated single type I cells from neonatal rat carotid bodies. Type I cells responded to graded hypoxic stimuli with graded [Ca2+]i rises. The percentage of cells responding was also dependent on the severity of the hypoxic stimulus. Raising CO2 from 5 to 10 or 20% elicited a significant increase in [Ca2+]i in the same cells as those that responded to hypoxia. Thus both stimuli can be sensed by each individual cell. When combinations of hypoxic and acidic stimuli were given simultaneously, the responses were invariably greater than the response to either stimulus given alone. Indeed, in most cases, the response to hypercapnia was slightly potentiated by hypoxia. These data provide the first evidence that the classic synergy between hypoxic and hypercapnic stimuli observed in the intact carotid body may, in part, be an inherent property of the type I cell.

Characteristics of carotid body chemosensitivity in NADPH oxidase-deficient mice

2002 ◽  
Vol 282 (1) ◽  
pp. C27-C33 ◽  
Author(s):  
L. He ◽  
J. Chen ◽  
B. Dinger ◽  
K. Sanders ◽  
K. Sundar ◽  
...  
Keyword(s):  
Tyrosine Hydroxylase ◽  
Nadph Oxidase ◽  
Carotid Body ◽  
Gene Knockout ◽  
Type I ◽  
Type I Cells ◽  
Carotid Bodies ◽  
Marker Antigen ◽  
I Cells

Various heme-containing proteins have been proposed as primary molecular O2 sensors for hypoxia-sensitive type I cells in the mammalian carotid body. One set of data in particular supports the involvement of a cytochrome b NADPH oxidase that is commonly found in neutrophils. Subunits of this enzyme have been immunocytochemically localized in type I cells, and diphenyleneiodonium, an inhibitor of the oxidase, increases carotid body chemoreceptor activity. The present study evaluated immunocytochemical and functional properties of carotid bodies from normal mice and from mice with a disrupted gp91 phagocytic oxidase (gp91 phox ) DNA sequence gene knockout (KO), a gene that codes for a subunit of the neutrophilic form of NADPH oxidase. Immunostaining for tyrosine hydroxylase, a signature marker antigen for type I cells, was found in groups or lobules of cells displaying morphological features typical of the O2-sensitive cells in other species, and the incidence of tyrosine hydroxylase-immunopositive cells was similar in carotid bodies from both strains of mice. Studies of whole cell K+currents also revealed identical current-voltage relationships and current depression by hypoxia in type I cells dissociated from normal vs. KO animals. Likewise, hypoxia-evoked increases in intracellular Ca2+ concentration were not significantly different for normal and KO type I cells. The whole organ response to hypoxia was evaluated in recordings of carotid sinus nerve activity in vitro. In these experiments, responses elicited by hypoxia and by the classic chemoreceptor stimulant nicotine were also indistinguishable in normal vs. KO preparations. Our data demonstrate that carotid body function remains intact after sequence disruption of the gp91 phox gene. These findings are not in accord with the hypothesis that the phagocytic form of NADPH oxidase acts as a primary O2 sensor in arterial chemoreception.

scholarly journals Immunohistochemical Characteristics of the Human Carotid Body in the Antenatal and Postnatal Periods of Development

2021 ◽  
Vol 22 (15) ◽  
pp. 8222
Author(s):  
Dmitry Otlyga ◽  
Ekaterina Tsvetkova ◽  
Olga Junemann ◽  
Sergey Saveliev
Keyword(s):  
Tyrosine Hydroxylase ◽  
Carotid Body ◽  
Nerve Fibers ◽  
Individual Development ◽  
Endocrine Function ◽  
Type I ◽  
Type I Cells ◽  
Carotid Bodies ◽  
I Cells ◽  
Human Carotid

The evolutionary and ontogenetic development of the carotid body is still understudied. Research aimed at studying the comparative morphology of the organ at different periods in the individual development of various animal species should play a crucial role in understanding the physiology of the carotid body. However, despite more than two centuries of study, the human carotid body remains poorly understood. There are many knowledge gaps in particular related to the antenatal development of this structure. The aim of our work is to study the morphological and immunohistochemical characteristics of the human carotid body in the antenatal and postnatal periods of development. We investigated the human carotid bodies from 1 embryo, 20 fetuses and 13 adults of different ages using samples obtained at autopsy. Immunohistochemistry revealed expression of βIII-tubulin and tyrosine hydroxylase in the type I cells and nerve fibers at all periods of ontogenesis; synaptophysin and PGP9.5 in the type I cells in some of the antenatal cases and all of the postnatal cases; 200 kDa neurofilaments in nerve fibers in some of the antenatal cases and all of the postnatal cases; and GFAP and S100 in the type II cells and Schwann cells in some of the antenatal cases and all of the postnatal cases. A high level of tyrosine hydroxylase in the type I cells was a distinctive feature of the antenatal carotid bodies. On the contrary, in the type I cells of adults, the expression of tyrosine hydroxylase was significantly lower. Our data suggest that the human carotid body may perform an endocrine function in the antenatal period, while in the postnatal period of development, it loses this function and becomes a chemosensory organ.

The identification of dopamine in the rabbit’s carotid body

1968 ◽  
Vol 170 (1019) ◽  
pp. 195-203 ◽  
Keyword(s):  
Carotid Body ◽  
Model System ◽  
Type I ◽  
Histochemical Technique ◽  
High Concentration ◽  
Metabolic Intermediate ◽  
Type I Cells ◽  
Carotid Bodies ◽  
Perivascular Nerves ◽  
I Cells

Application of the Falck & Hillarp histochemical technique to the rabbit carotid body reveals three fluorescent structures: brilliantly fluorescent Type I cells, varicose perivascular nerves, and weakly fluorescent non-varicose fibres. The Type I cell fluorescence is similar to that of a dopamine model system and has the appropriate activation and emission maxima. A catecholamine, identified as dopamine, has been extracted from homogenized carotid bodies, and estimated by the trihydroxyindole procedure. The concentration of the dopamine in the carotid body is estimated to be 20 to 40 μ g/g. This is very much greater than that of the noradrenaline present, of which there is about 1·5 μ g/g. The fluorescence of the Type I cells is attributed to the dopamine and it is suggested that the amine may be granule-bound. The unusually high concentration of dopamine could imply that it is not merely a metabolic intermediate in the carotid body.

Postnatal maturation of carotid body and type I cell chemoreception in the rat

1999 ◽  
Vol 276 (5) ◽  
pp. L875-L884 ◽  
Author(s):  
Owen S. Bamford ◽  
Laura M. Sterni ◽  
Michael J. Wasicko ◽  
Marshall H. Montrose ◽  
John L. Carroll
Keyword(s):  
Carotid Body ◽  
Carotid Sinus ◽  
Type I ◽  
Carotid Sinus Nerve ◽  
Postnatal Maturation ◽  
Cell Responses ◽  
Type I Cells ◽  
Intracellular Ca ◽  
I Cells

The site of postnatal maturation of carotid body chemoreception is unclear. To test the hypothesis that maturation occurs synchronously in type I cells and the whole carotid body, the development of changes in the intracellular Ca2+ concentration responses to hypoxia, CO2, and combined challenges was studied with fluorescence microscopy in type I cells and compared with the development of carotid sinus nerve (CSN) responses recorded in vitro from term fetal to 3-wk animals. Type I cell responses to all challenges increased between 1 and 8 days and then remained constant, with no multiplicative O2-CO2interaction at any age. The CSN response to hypoxia also matured by 8 days, but CSN responses to CO2 did not change significantly with age. Multiplicative O2-CO2interaction occurred in the CSN response at 2–3 wk but not in younger groups. We conclude that type I cell maturation underlies maturation of the CSN response to hypoxia. However, because development of responses to CO2 and combined hypoxia-CO2 challenges differed between type I cells and the CSN, responses to these stimuli must mature at other, unidentified sites within the developing carotid body.

scholarly journals Cellular mechanisms involved in carotid body inhibition produced by atrial natriuretic peptide

2000 ◽  
Vol 278 (4) ◽  
pp. C845-C852 ◽  
Author(s):  
L. He ◽  
B. Dinger ◽  
S. Fidone
Keyword(s):  
Atrial Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Carotid Body ◽  
Type I ◽  
Cellular Mechanisms ◽  
Channel Proteins ◽  
Type I Cells ◽  
Intracellular Ca ◽  
I Cells ◽  
Atrial Natriuretic

Atrial natriuretic peptide (ANP) and its analog, atriopeptin III (APIII), inhibit carotid body chemoreceptor nerve activity evoked by hypoxia. In the present study, we have examined the hypothesis that the inhibitory effects of ANP and APIII are mediated by cyclic GMP and protein kinase G (PKG) via the phosphorylation and/or dephosphorylation of K+ and Ca2+ channel proteins that are involved in regulating the response of carotid body chemosensory type I cells to low-O2 stimuli. In freshly dissociated rabbit type I cells, we examined the effects of a PKG inhibitor, KT-5823, and an inhibitor of protein phosphatase 2A (PP2A), okadaic acid (OA), on K+ and Ca2+ currents. We also investigated the effects of these specific inhibitors on intracellular Ca2+ concentration and carotid sinus nerve (CSN) activity under normoxic and hypoxic conditions. Voltage-dependent K+ currents were depressed by hypoxia, and this effect was significantly reduced by 100 nM APIII. The effect of APIII on this current was reversed in the presence of either 1 μM KT-5823 or 100 nM OA. Likewise, these drugs retarded the depression of voltage-gated Ca2+ currents induced by APIII. Furthermore, APIII depressed hypoxia-evoked elevations of intracellular Ca2+, an effect that was also reversed by OA and KT-5823. Finally, CSN activity evoked by hypoxia was decreased in the presence of 100 nM APIII, and was partially restored when APIII was presented along with 100 nM OA. These results suggest that ANP initiates a cascade of events involving PKG and PP2A, which culminates in the dephosphorylation of K+ and Ca2+ channel proteins in the chemosensory type I cells.

Immunohistochemical demonstration of four subunits of neutrophil NAD(P)H oxidase in type I cells of carotid body

1995 ◽  
Vol 78 (5) ◽  
pp. 1904-1909 ◽  
Author(s):  
W. Kummer ◽  
H. Acker
Keyword(s):  
Hydrogen Peroxide ◽  
Carotid Body ◽  
Oxygen Sensor ◽  
Neutrophil Granulocytes ◽  
Type I ◽  
Body Type ◽  
Type I Cells ◽  
Carotid Bodies ◽  
Sensor Protein ◽  
I Cells

We demonstrate, by means of immunohistochemistry, that type I cells of human, guinea pig, and rat carotid bodies react with antisera raised against the subunits p22phox, gp91phox, p47phox, and p67phox of the NAD(P)H oxidase isolated from human neutrophil granulocytes. The findings support previous photometric studies that indicate that carotid body type I cells possess a putative oxygen sensor protein that is similar to the neutrophil NAD(P)H oxidase and consists of a hydrogen peroxide generating low-potential cytochrome b558 with cofactors regulating the electron transfer to oxygen.

scholarly journals Effect of p47phox gene deletion on ROS production and oxygen sensing in mouse carotid body chemoreceptor cells

2005 ◽  
Vol 289 (6) ◽  
pp. L916-L924 ◽  
Author(s):  
L. He ◽  
B. Dinger ◽  
K. Sanders ◽  
J. Hoidal ◽  
A. Obeso ◽  
...  
Keyword(s):  
Nadph Oxidase ◽  
Carotid Body ◽  
Oxidase Inhibitor ◽  
Type I ◽  
Ros Production ◽  
Normal Cells ◽  
Type I Cells ◽  
Nadph Oxidase Inhibitor ◽  
Intracellular Ca ◽  
I Cells

Membrane potential in oxygen-sensitive type I cells in carotid body is controlled by diverse sets of voltage-dependent and -independent K+ channels. Coupling of Po2 to the open-closed state of channels may involve production of reactive oxygen species (ROS) by NADPH oxidase. One hypothesis suggests that ROS are produced in proportion to the prevailing Po2 and a subset of K+ channels closes as ROS levels decrease. We evaluated ROS levels in normal and p47 phox gene-deleted [NADPH oxidase knockout (KO)] type I cells using the ROS-sensitive dye dihydroethidium (DHE). In normal cells, hypoxia elicited an increase in ROS, which was blocked by the specific NADPH oxidase inhibitor 4-(2-aminoethyl)-benzenesulfonyl fluoride (AEBSF, 3 mM). KO type I cells did not respond to hypoxia, but the mitochondrial uncoupler azide (5 μM) elicited increased fluorescence in both normal and KO cells. Hypoxia had no effect on ROS production in sensory and sympathetic neurons. Methodological control experiments showed that stimulation of neutrophils with a cocktail containing the chemotactic peptide N-formyl-Met-Leu-Phe (1 μM), arachidonic acid (10 μM), and cytochalasin B (5 μg/ml) elicited a rapid increase in DHE fluorescence. This response was blocked by the NADPH oxidase inhibitor diphenyleneiodonium (10 μM). KO neutrophils did not respond; however, azide (5 μM) elicited a rapid increase in fluorescence. Physiological studies in type I cells demonstrated that hypoxia evoked an enhanced depression of K+ current and increased intracellular Ca2+ levels in KO vs. normal cells. Moreover, AEBSF potentiated hypoxia-induced increases in intracellular Ca2+ and enhanced the depression of K+ current in low O2. Our findings suggest that local compartmental increases in oxidase activity and ROS production inhibit the activity of type I cells by facilitating K+ channel activity in hypoxia.

Autocrine and paracrine actions of ATP in rat carotid body

2012 ◽  
Vol 90 (6) ◽  
pp. 705-711 ◽  
Author(s):  
Amy Tse ◽  
Lei Yan ◽  
Andy K. Lee ◽  
Frederick W. Tse
Keyword(s):  
Carotid Body ◽  
Cellular Damage ◽  
Type I ◽  
Glomus Cells ◽  
Sustentacular Cells ◽  
Arterial Blood ◽  
Carotid Bodies ◽  
Intracellular Ca ◽  
Paracrine Actions ◽  
I Cells

Carotid bodies are peripheral chemoreceptors that detect lowering of arterial blood O2 level. The carotid body comprises clusters of glomus (type I) cells surrounded by glial-like sustentacular (type II) cells. Hypoxia triggers depolarization and cytosolic [Ca2+] ([Ca2+]i) elevation in glomus cells, resulting in the release of multiple transmitters, including ATP. While ATP has been shown to be an important excitatory transmitter in the stimulation of carotid sinus nerve, there is considerable evidence that ATP exerts autocrine and paracrine actions in carotid body. ATP acting via P2Y1 receptors, causes hyperpolarization in glomus cells and inhibits the hypoxia-mediated [Ca2+]i rise. In contrast, adenosine (an ATP metabolite) triggers depolarization and [Ca2+]i rise in glomus cells via A2A receptors. We suggest that during prolonged hypoxia, the negative and positive feedback actions of ATP and adenosine may result in an oscillatory Ca2+ signal in glomus cells. Such mechanisms may allow cyclic release of transmitters from glomus cells during prolonged hypoxia without causing cellular damage from a persistent [Ca2+]i rise. ATP also stimulates intracellular Ca2+ release in sustentacular cells via P2Y2 receptors. The autocine and paracrine actions of ATP suggest that ATP has important roles in coordinating chemosensory transmission in the carotid body.

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