Voltage-gated K⁺ (Kv) channels play a critical role in the excitation-contraction coupling of arterial smooth muscle cells (Cheong et al. 2001a,b). A range of studies have indicated that the many genes encoding Kv channels may be differentially expressed in the vasculature, possibly because the different Kv channels serve different functional needs. However, quantitative data on expression are lacking. We used quantitative real-time RT-PCR to provide such data for murine aorta and first-order mesenteric artery.

Male 8-week-old C57/BL6 mice were killed humanely. Dissected arteries were endothelium-denuded by luminal perfusion with mild detergent. Aortic adventitia were removed by dissection. Kv RNA abundance was calculated as a ratio relative to β-actin RNA and taking into account primer-specific PCR efficiencies. Data are expressed as means ± S.E.M. and comparisons were made by Student’s unpaired t test.

Levels of β-actin RNA (expressed as PCR crossing points, CP) were not significantly different between aortic medial layer, denuded aorta or denuded mesenteric artery (Cp 21.88 ± 0.32, 22.94 ± 0.20 and 22.18 ± 0.51; P > 0.05, n = 4-6). No significant differences were observed between aortae with or without adventitia or endothelium for all the Kv RNA species indicated below (n = 4, P > 0.05). Strikingly, Kv RNA levels were, however, orders of magnitude higher (P < 0.05 and n = 4 in each case) in mesenteric artery compared with aorta: Kv1.1 (1.46 ± 0.16 cf. 0.010 ± 0.002), Kv1.2 (0.06 ± 0.01 cf. 0.003 ± 0.001), Kv1.3 (0.05 ± 0.01 cf. 0.002 ± 0.000), Kv1.5 (0.03 ± 0.01 cf. 0.001 ± 0.001), and Kv2.1 (0.18 ± 0.03 cf. 0.044 ± 0.001). The RNA level for the Slo1 gene encoding the α-subunit of the large conductance calcium-activated K⁺ channel was by contrast slightly, but not significantly (P > 0.05), less in mesenteric artery compared with aorta (0.43 ± 0.10 cf. 0.69 ± 0.11, n = 4 for each).

The data show that there is quantitatively much more expression of Kv channel genes in a resistance compared with a conduit artery. This is consistent with our hypothesis that Kv channel expression and function is important in resistance arteries and arterioles, and that relative and specific Kv channel gene expression patterns may have particular significance in the physiological control of blood pressure.

This work was supported by the Medical Research Council and the British Heart Foundation.