Do K 7.1 channels contribute to control of arterial vascular tone?

BACKGROUND AND PURPOSE

K 7.1 voltage-gated potassium channels are expressed in vascular smooth muscle cells (VSMC) of diverse arteries, including mesenteric arteries. Based on pharmacological evidence using R-L3 (K 7.1 channel opener), HMR1556, chromanol 293B (K 7.1 channel blockers), stimulation of these channels has been suggested to evoke profound relaxation in various vascular beds of rats. However, the specificity of these drugs in vivo is uncertain.

EXPERIMENTAL APPROACH

We used Kcnq1 mice and pharmacological tools to determine whether K 7.1 channels play a role in the regulation of arterial tone.

KEY RESULTS

R-L3 produced similar concentration-dependent relaxations (EC  ~ 1.4 μM) of arteries from wild-type (Kcnq1 ) and Kcnq1 mice, pre-contracted with either phenylephrine or 60 mM KCl. This relaxation was not affected by 10 μM chromanol 293B, 10 μM HMR1556 or 30 μM XE991 (pan-K 7 channel blocker). The anti-contractile effects of the perivascular adipose tissue (PVAT) were normal in Kcnq1 arteries. Chromanol 293B and HMR1556 did not affect the anti-contractile effects of (PVAT). Isolated VSMCs from Kcnq1 mice exhibited normal peak K currents. The K 7.2-5 channel opener retigabine caused similar relaxations in Kcnq1 and wild-type vessels.

CONCLUSION AND IMPLICATIONS

We conclude that K 7.1 channels were apparently not involved in the control of arterial tone by α -adrenoceptor agonists and PVAT. In addition, R-L3 is an inappropriate pharmacological tool for studying the function of native vascular K 7.1 channels in mice.