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Universidad de Valladolid y Consejo Superior de Investigaciones Científicas (CSIC), Departamento de Bioquímica y Biología Molecular y Fisiología e Instituto de Biología y Genética Molecular (IBGM), Facultad de Medicina, Valladolid, Spain
As there are wide interspecies variations in the molecular nature of the O2-sensitive Kv channels in arterial chemoreceptors, we have characterized the expression of these channels and their hypoxic sensitivity in the mouse carotid body (CB). CB chemoreceptor cells were obtained from a transgenic mouse expressing green fluorescent protein (GFP) under the control of tyrosine hydroxylase (TH) promoter. Immunocytochemical identification of TH in CB cell cultures reveals a good match with GFP-positive cells. Furthermore, these cells show an increase in [Ca2+]i in response to low PO2, demonstrating their ability to engender a physiological response. Whole-cell experiments demonstrated slow-inactivating K+ currents with activation threshold around –30 mV and a bi-exponential kinetic of deactivation (
of 6.24 ± 0.52 and 32.85 ± 4.14 ms). TEA sensitivity of the currents identified also two different components (IC50 of 17.8 ± 2.8 and 940.0 ± 14.7 µM). Current amplitude decreased reversibly in response to hypoxia, which selectively affected the fast deactivating component. Hypoxic inhibition was also abolished in the presence of low (10–50 µM) concentrations of TEA, suggesting that O2 interacts with the component of the current most sensitive to TEA. The kinetic and pharmacological profile of the currents suggested the presence of Kv2 and Kv3 channels as their molecular correlates, and we have identified several members of these two subfamilies by single-cell PCR and immunocytochemistry. This report represents the first functional and molecular characterization of Kv channels in mouse CB chemoreceptor cells, and strongly suggests that O2-sensitive Kv channels in this preparation belong to the Kv3 subfamily.
(Received 10 February 2004;
accepted after revision 16 March 2004;
first published online 19 March 2004)
Corresponding author M. Teresa Pérez-García: Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Universidad de Valladolid., C/Ramón y Cajal 7, 47005 Valladolid, Spain. Email: tperez{at}ibgm.uva.es
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