T‐type calcium channels in carotid body oxygen sensing (889.1)

Previous studies showed that low voltage gated T‐type Ca 2+ channels play an important role in hypoxia‐evoked catecholamine secretion from adrenal chromaffin cells. The objective of the present study was to investigate whether T‐type Ca 2+ channels contribute to hypoxic sensing by the carotid body, a key sensory organ for detecting arterial blood O 2 levels. Real time quantitative PCR analysis of rat carotid body revealed relatively high levels of α 1H as compared to α 1G and α 1I subunits of T‐type Ca 2+ channels. Immunocytochemical analysis showed much of the α 1H protein in glomus cells. Mibefradil (1µM), a T‐type Ca 2+ channel blocker significantly attenuated the carotid body sensory and glomus cell secretory and [Ca 2+ ] i responses to hypoxia. Similar attenuation of glomus cell secretory as well as [Ca 2+ ] i responses were also seen in α 1H knockout mice. These results demonstrate that T‐type Ca 2+ channels contribute to carotid body and glomus cells response to hypoxia. Grant Funding Source : Supported by NIH‐HL‐90554