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Background— Angioplasty stimulates proliferation and migration of vascular smooth muscle cells (VSMC), leading to neointimal thickening and vascular restenosis. In a rat model of balloon catheter injury (BCI), we investigated whether alterations in expression of Ca²⁺-activated K⁺ channels (K_Ca) contribute to intimal hyperplasia and vascular restenosis.

Methods and Results— Function and expression of K_Ca in mature medial and neointimal VSMC were characterized in situ by combined single-cell RT-PCR and patch-clamp analysis. Mature medial VSMC exclusively expressed large-conductance K_Ca (BK_Ca) channels. Two weeks after BCI, expression of BK_Ca was significantly reduced in neointimal VSMC, whereas expression of intermediate-conductance K_Ca (IKCa1) channels was upregulated. In the aortic VSMC cell line, A7r5 epidermal growth factor (EGF) induced IKCa1 upregulation and EGF …