Expression of voltage-dependent K+ channel genes in mesenteric artery smooth muscle cells

Molecular basis of native voltage-dependent K+ (Kv) channels in smooth muscle cells (SMCs) from rat mesenteric arteries was investigated. The whole cell patch-clamp study revealed that a 4-aminopyridine-sensitive delayed rectifier K+ current (I-K) was the predominant K+ conductance in these cells. A systematic screening of the expression of 18 Kv channel genes using RT-PCR technique showed that six I-K-encoding genes (Kv1.2, Kv1.3, Kv1.5, Kv2.1, Kv2.2, and Kv3.2) were expressed in mesenteric artery. Although no transient outward Kv currents (I-A) were recorded in the studied SMCs, transcripts of multiple I-A-encoding genes, including Kv1.4, Kv3.3, Kv3.4, Kv4.1, Kv4.2, and Kv4.3 as well as I-A-facilitating Kv beta-subunits (Kv beta 1, Kv beta 2, and Kv beta 3), were detected in mesenteric arteries. Western blot analysis demonstrated that four I-K-related Kv channel proteins (Kv1.2, Kv1.3, Kv1.5, and Kv2.1) were detected in mesenteric artery tissues. The presence of Kv1.2, Kv1.3, Kv1.5, and Kv2.1 channel proteins in isolated SMCs was further confirmed by immunocytochemistry study. Our results suggest that the native I-K in rat mesenteric artery SMCs might be generated by heteromultimerization of Kv genes.