OBJECTIVE: To determine whether, in native pulmonary arterial smooth muscle cells (PASMC), K(V)2.1 delayed-rectifying K(+) channels are central to the process of hypoxic pulmonary vasoconstriction. METHODS: In this study, we tested for the presence of K(V)2.1 channel transcripts in rat small pulmonary arteries using RT-PCR, and for the protein itself using immunolocalisation. The contribution of K(V)2.1 channels to whole-cell K(V) currents (I(KV)) and their role in hypoxic inhibition of I(KV) in native PASMC was investigated utilising patch-clamp recordings. RESULTS: K(V)2.1 mRNA expression and AbK(V)2.1 (anti-K(V)2.1 antibody) protein immunoreactivity were both present in small pulmonary arteries. Dialysis of PASMC with AbK(V)2.1 significantly attenuated I(KV) by 67% at +50 mV. Hypoxia ( approximately 20-30 mmHg) inhibited I(KV) by approximately 70% at +50 mV. Ablation of currents associated with K(V)2.1 using AbK(V)2.1 caused a marked reduction in the amplitude of I(KV). Hypoxia in the presence of the antibody did not affect the magnitude of I(KV). CONCLUSIONS: These results indicate that K(V)2.1 channel subunits exist within small pulmonary arteries and conduct a significant part of I(KV) within native PASMC. Furthermore, application of AbK(V)2.1 abolishes hypoxic inhibition of I(KV) in native PASMC suggesting that K(V)2.1 channels play a pivotal role in mediating hypoxic pulmonary vasoconstriction.
OBJECTIVE: To determine whether, in native pulmonary arterial smooth muscle cells (PASMC), K(V)2.1 delayed-rectifying K(+) channels are central to the process of hypoxic pulmonary vasoconstriction. METHODS: In this study, we tested for the presence of K(V)2.1 channel transcripts in rat small pulmonary arteries using RT-PCR, and for the protein itself using immunolocalisation. The contribution of K(V)2.1 channels to whole-cell K(V) currents (I(KV)) and their role in hypoxic inhibition of I(KV) in native PASMC was investigated utilising patch-clamp recordings. RESULTS:K(V)2.1 mRNA expression and AbK(V)2.1 (anti-K(V)2.1 antibody) protein immunoreactivity were both present in small pulmonary arteries. Dialysis of PASMC with AbK(V)2.1 significantly attenuated I(KV) by 67% at +50 mV. Hypoxia ( approximately 20-30 mmHg) inhibited I(KV) by approximately 70% at +50 mV. Ablation of currents associated with K(V)2.1 using AbK(V)2.1 caused a marked reduction in the amplitude of I(KV). Hypoxia in the presence of the antibody did not affect the magnitude of I(KV). CONCLUSIONS: These results indicate that K(V)2.1 channel subunits exist within small pulmonary arteries and conduct a significant part of I(KV) within native PASMC. Furthermore, application of AbK(V)2.1 abolishes hypoxic inhibition of I(KV) in native PASMC suggesting that K(V)2.1 channels play a pivotal role in mediating hypoxic pulmonary vasoconstriction.