Expression and Immunolocalization of Endothelin Peptides and Its Receptors, ET_A AND ET_B, in the Carotid Body Exposed to Chronic Intermittent Hypoxia

Sergio Rey ¹, Jenny Corthorn ¹, Cecilia Chacón ¹ and Rodrigo Iturriaga ^1*

¹ Laboratorio de Neurobiología, Facultad de Ciencias Biológicas (SR,RI) and Departamento de Nefrología y Centro de Investigaciones Médicas, Facultad de Medicina (SR,JC,CC), Pontificia Universidad Católica de Chile, Santiago, Chile

^* To whom correspondence should be addressed. E-mail: riturriaga{at}bio.puc.cl.

Submitted on August 18, 2006
Accepted on 28 September 2006

	Abstract

Increased levels of endothelin-1 (ET-1) in the carotid body (CB) contribute to the enhancement of chemosensory responses to acute hypoxia in cats exposed to chronic intermittent hypoxia (CIH). However, it is not known if the ET receptors type A (ET_A-R) and B (ET_B-R) are upregulated. Thus, we studied the expression and localization of ET_A-R and ET_B-R using Western blot and immunohistochemistry in CBs from cats exposed to cyclic hypoxic episodes, repeated during 8 hr for 4 days. In addition, we determined if ET-1 is expressed in the chemoreceptor cells using double immunofluorescence for ET-1 and tyrosine hydroxylase (TH). We found that ET-1 expression was ubiquitous in the blood vessels and CB parenchyma, although double ET-1 and TH positive chemoreceptor cells were mostly found in the parenchyma. ET_A-R was expressed in most chemoreceptor cells and blood vessels of the CB vascular pole. ET_B-R was expressed in chemoreceptor cells, in parenchymal capillaries and blood vessels of the vascular pole. CIH upregulated ET_B-R expression by 2.1 (Western blot) and 1.6-fold (immunohistochemistry), but did not change ET_A-R expression. Present results suggest that ET-1, ET_A-R and ET_B-R are involved in the enhanced CB chemosensory responses to acute hypoxia induced by CIH.

Key Words: carotid body, intermittent hypoxia, endothelin receptors

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