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Article: Carotid body AT4 receptor expression and its upregulation in chronic hypoxia

TitleCarotid body AT4 receptor expression and its upregulation in chronic hypoxia
Authors
KeywordsAngiotensin IV
Angiotensin IV receptor
Chemoreceptor
Type-I cells
Issue Date2007
PublisherBentham Open. The Journal's web site is located at http://www.bentham.org/open/tocmj/
Citation
The Open Cardiovascular Medicine Journal, 2007, v. 1, p. 1-7 How to Cite?
AbstractHypoxia regulates the local expression of angiotensin-generating system in the rat carotid body and the me-tabolite angiotensin IV (Ang IV) may be involved in the modulation of carotid body function. We tested the hypothesis that Ang IV-binding angiotensin AT(4) receptors play a role in the adaptive change of the carotid body in hypoxia. The expression and localization of Ang IV-binding sites and AT(4) receptors in the rat carotid bodies were studied with histochemistry. Specific fluorescein-labeled Ang IV binding sites and positive staining of AT(4) immunoreactivity were mainly found in lobules in the carotid body. Double-labeling study showed the AT(4) receptor was localized in glomus cells containing tyrosine hydroxylase, suggesting the expression in the chemosensitive cells. Intriguingly, the Ang IV-binding and AT(4) immunoreactivity were more intense in the carotid body of chronically hypoxic (CH) rats (breathing 10% oxygen for 4 weeks) than the normoxic (Nx) control. Also, the protein level of AT(4) receptor was doubled in the CH comparing with the Nx group, supporting an upregulation of the expression in hypoxia. To examine if Ang IV induces intracellular Ca(2+) response in the carotid body, cytosolic calcium ([Ca(2+)](i)) was measured by spectrofluorimetry in fura-2-loaded glomus cells dissociated from CH and Nx carotid bodies. Exogenous Ang IV elevated [Ca(2+)](i) in the glomus cells and the Ang IV response was significantly greater in the CH than the Nx group. Hence, hypoxia induces an upregulation of the expression of AT(4) receptors in the glomus cells of the carotid body with an increase in the Ang IV-induced [Ca(2+)]i elevation. This may be an additional pathway enhancing the Ang II action for the activation of chemoreflex in the hypoxic response during chronic hypoxia.
Persistent Identifierhttp://hdl.handle.net/10722/81236
ISSN
2015 SCImago Journal Rankings: 0.321
PubMed Central ID

 

DC FieldValueLanguage
dc.contributor.authorFung, MLen_HK
dc.contributor.authorLam, SYen_HK
dc.contributor.authorWong, TPen_HK
dc.contributor.authorTjong, YWen_HK
dc.contributor.authorLeung, PSen_HK
dc.date.accessioned2010-09-06T08:15:22Z-
dc.date.available2010-09-06T08:15:22Z-
dc.date.issued2007en_HK
dc.identifier.citationThe Open Cardiovascular Medicine Journal, 2007, v. 1, p. 1-7en_HK
dc.identifier.issn1874-1924en_HK
dc.identifier.urihttp://hdl.handle.net/10722/81236-
dc.description.abstractHypoxia regulates the local expression of angiotensin-generating system in the rat carotid body and the me-tabolite angiotensin IV (Ang IV) may be involved in the modulation of carotid body function. We tested the hypothesis that Ang IV-binding angiotensin AT(4) receptors play a role in the adaptive change of the carotid body in hypoxia. The expression and localization of Ang IV-binding sites and AT(4) receptors in the rat carotid bodies were studied with histochemistry. Specific fluorescein-labeled Ang IV binding sites and positive staining of AT(4) immunoreactivity were mainly found in lobules in the carotid body. Double-labeling study showed the AT(4) receptor was localized in glomus cells containing tyrosine hydroxylase, suggesting the expression in the chemosensitive cells. Intriguingly, the Ang IV-binding and AT(4) immunoreactivity were more intense in the carotid body of chronically hypoxic (CH) rats (breathing 10% oxygen for 4 weeks) than the normoxic (Nx) control. Also, the protein level of AT(4) receptor was doubled in the CH comparing with the Nx group, supporting an upregulation of the expression in hypoxia. To examine if Ang IV induces intracellular Ca(2+) response in the carotid body, cytosolic calcium ([Ca(2+)](i)) was measured by spectrofluorimetry in fura-2-loaded glomus cells dissociated from CH and Nx carotid bodies. Exogenous Ang IV elevated [Ca(2+)](i) in the glomus cells and the Ang IV response was significantly greater in the CH than the Nx group. Hence, hypoxia induces an upregulation of the expression of AT(4) receptors in the glomus cells of the carotid body with an increase in the Ang IV-induced [Ca(2+)]i elevation. This may be an additional pathway enhancing the Ang II action for the activation of chemoreflex in the hypoxic response during chronic hypoxia.-
dc.languageengen_HK
dc.publisherBentham Open. The Journal's web site is located at http://www.bentham.org/open/tocmj/en_HK
dc.relation.ispartofThe Open Cardiovascular Medicine Journalen_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.subjectAngiotensin IV-
dc.subjectAngiotensin IV receptor-
dc.subjectChemoreceptor-
dc.subjectType-I cells-
dc.titleCarotid body AT4 receptor expression and its upregulation in chronic hypoxiaen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=1874-1924&volume=1&spage=1&epage=7&date=2007&atitle=Carotid+body+AT4+receptor+expression+and+its+upregulation+in+chronic+hypoxiaen_HK
dc.identifier.emailFung, ML: fungml@hkucc.hku.hken_HK
dc.identifier.emailLam, SY: sylvia.lam@alumni.cuhk.neten_HK
dc.identifier.emailTjong, YW: jefftjong@yahoo.com.hken_HK
dc.identifier.authorityFung, ML=rp00433en_HK
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.2174/1874192400701010001-
dc.identifier.pmid18949084-
dc.identifier.pmcidPMC2570565-
dc.identifier.hkuros128802en_HK
dc.identifier.volume1-
dc.identifier.spage1-
dc.identifier.epage7-
dc.publisher.placeNetherlands-

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