Kv channel subunit expression in rat pulmonary arteries

Hypoxic pulmonary vasoconstriction (HPV) is a mechanism whereby capillary perfusion is modulated to match alveolar ventilation by diverting blood flow away from poorly ventilated regions of the lung. K+ channels, sensitive to changes in oxygen tension, are thought to play a pivotal role in initiating contraction of pulmonary arterial smooth muscle cells. However, the specific channel subtypes involved have not yet been identified. Using RT-PCR, we have investigated the expression of delayed rectifying (Kv) channel mRNA in rat main and small pulmonary arteries and, for comparison, the systemic mesenteric artery. We have identified and fully sequenced a rat Kv9.2 cDNA and also demonstrated the presence of Kv1.7 and Kv4.1. The presence and relative distribution of Kv1.2, Kv1.5, Kv2.1, and Kv9 mRNA is consistent with the proposed contribution of these subunits to oxygen sensing by K channels, previously described in pulmonary arteries. Our data addresses the controversy relating to the likely distribution of Kv channels involved in oxygen sensing without necessarily implying that such subunits are directly responsible for this process. The differential expression of other subunits, particularly Kv4, indicates that these too may have a role in HPV, revealing the need for further biophysical evaluation of these channel subtypes.