The carotid body (CB) is a primary chemosensory organ for arterial
hypoxia. Inhibition of K channels in chemosensory glomus cells (GCs) are considered to be responsible for hypoxic chemoreception and/or chemotransduction of the CB. Hypoxic sensitivity of large-conductance
calcium-activated K (
BK) channels has been established in the rat CB. Our previous work has shown the
BK channel β2 subunits are more expressed in the CB of the DBA/2J mouse than that of the A/J mouse. Because the DBA/2J mouse is more sensitive to
hypoxia than the A/J mouse, our general hypothesis is that
BK channels play a role in the sensitivity of the mouse CB to mild
hypoxia. We performed vigorous analysis of the gene expression of α, β2, and β4 subunits of
BK channels in the CB. We found that α and β2 subunits were expressed more in the CB of the DBA/2J mice than that of the A/J mice. No differences were found in the β4 subunit expression. These differences were not seen in the neighboring tissues, the superior cervical ganglion and the carotid artery, suggesting that the differences are CB specific. Further, the sensitivity of
BK channels in GCs to mild
hypoxia was examined in patch clamp experiments using undissociated CBs.
Iberiotoxin significantly inhibited K current of GCs in the DBA/2J mice, but not in the A/J mice. When reducing PO(2) to ∼70 mmHg, K current reversibly decreased in GCs of the DBA/2J, but not of the A/J mice. In the presence of
iberiotoxin, mild
hypoxia did not inhibit K current in either strains. Thus, the data suggest that
BK channels in GCs of the DBA/2J mice are sensitive to mild
hypoxia. Differential expression of
BK channel β subunits in the CBs may, at least in part, explain the different hypoxic sensitivity in these mouse strains.