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Molecular identification and functional role of voltage‐gated sodium channels in rat carotid body chemoreceptor cells. Regulation of expression by chronic hypoxia in vivo
Author(s) -
Caceres Ana I.,
Obeso Ana,
Gonzalez Constancio,
Rocher Asuncion
Publication year - 2007
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2007.04465.x
Subject(s) - veratridine , carotid body , chemoreceptor , hypoxia (environmental) , tetrodotoxin , endocrinology , medicine , biology , sodium channel , gene isoform , microbiology and biotechnology , sodium , chemistry , biochemistry , receptor , stimulation , oxygen , gene , organic chemistry
We have assessed the expression, molecular identification and functional role of Na + channels (Na v ) in carotid bodies (CB) obtained from normoxic and chronically hypoxic adult rats. Veratridine evoked release of catecholamines (CA) from an in vitro preparation of intact CBs obtained from normoxic animals, the response being Ca 2+ and Na + ‐dependent and sensitive to tetrodotoxin (TTX). TTX inhibited by 25–50% the CA release response evoked by graded hypoxia. Immunoblot assays demonstrated the presence of Na v α‐subunit ( c. 220 kDa) in crude homogenates from rat CBs, being evident an up‐regulation (60%) of this protein in the CBs obtained from chronically hypoxic rats (10% O 2 ; 7 days). This up‐regulation was accompanied by an enhanced TTX‐sensitive release response to veratridine, and by an enhanced ventilatory response to acute hypoxic stimuli. RT‐PCR studies demonstrated the expression of mRNA for Na v 1.1, Na v 1.2, Na v 1.3, Na v 1.6 and Na v 1.7 isoforms. At least three isoforms, Na v 1.1, Na v 1.3 and Na v 1.6 co‐localized with tyrosine hydroxylase in all chemoreceptor cells. RT‐PCR and immunocytochemistry indicated that Na v 1.1 isoform was up‐regulated by chronic hypoxia in chemoreceptor cells. We conclude that Na v up‐regulation represents an adaptive mechanism to increase chemoreceptor sensitivity during acclimatization to sustained hypoxia as evidenced by enhanced ventilatory responses to acute hypoxic tests.