Differential expression of KV channel α- and β-subunits in the bovine pulmonary arterial circulation

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Abstract
Resistance pulmonary arteries constrict in response to hypoxia, whereas conduit pulmonary arteries typically do not respond or dilate slightly. One proposed mechanism for this differential response is the variable expression of pulmonary arterial smooth muscle cell voltage-gated K+ (KV) channel subunits (Kv1.2, Kv2.1, Kv1.5, and Kv3.1b) shown to be O2 sensitive in heterologous expression systems. In this study, immunoblotting and immunohistochemistry were used to examine the expression of KV channel α- and β-subunits in the bovine pulmonary arterial circulation to determine whether differential KVchannel subunit distribution is responsible for the distinct sensitivities of pulmonary arteries to hypoxia. Surprisingly, there was little difference in the expression levels of Kv1.2, Kv1.5, and Kv2.1 between conduit and resistance pulmonary arteries. In contrast, expression of the Kv3.1b α-subunit and Kvβ.1, Kvβ1.2, and Kvβ1.3 accessory subunits dramatically increased along the pulmonary arterial tree. The differential expression of all the β-subunits but of only one of the putative O2-sensitive α-subunits suggests that the α-subunits alone are not the O2 sensors but further implicates the auxiliary β-subunits in pulmonary arterial O2 sensing.

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