Molecular Basis of Dysfunctional K(subscript V) Channels in Small Coronary Artery Smooth Muscle Cells of Streptozotocin-Induced Diabetic Rats

Qiang Chai；Xiao-Qun Xu；Qing Jia；Qiang Dong；Zhi-Xiang Liu；Wei-Dong Zhang；Lian-Bi Chen

streptozotocin-induced diabetes of rat ； small coronary artery smooth muscle cells ； voltage dependent potassium channel ； mRNA ； Western blot ； immunohistochemistry

The Chinese Journal of Physiology

50卷4期（2007 / 08 / 31）

171 - 177

英文

We have previously shown that diabetes impaired cAMP-mediated endothelium independent vasodilation of rat small coronary arteries. Inhibition of K(subscript V) channel activity plays an important role in the decrease of cAMP mediated vasodilation. The present study investigated the effect of streptozotocin (STZ)-induced diabetes on mRNA and protein expressions of K(subscript V)1.2 and K(subscript V)1.5 channels in vascular smooth muscle cells of rat small coronary artery using RT-PCR, Western blot and immunohistochemistry methods. STZ-induced diabetes obviously impaired mRNA expression of K(subscript V)1.2 and K(subscript V)1.5 channel. The mRNA levels of K(subscript V)1.2 channel were 0.65±0.08 and 1.02±0.17 in STZ rats and control rats, respectively (n=7, P＜0.05). Whereas the levels of K(subscript V)1.5 channel were 0.58±0.05 and 0.94±0.13 in STZ rats and control rats, respectively (n=7, P＜0.05). Western blotting analysis showed that protein expression of K(subscript V)1.2 channel was decreased significantly but not K(subscript V)1.5 channel. Protein expressions of K(subscript V)1.2 channel were 0.49±0.04 and 0.70±0.06 in STZ rats and control rats, respectively (n=5, P＜0.05), but those of K(subscript V)1.5 channel were 0.61±0.12 and 0.59±0.14 in STZ rats and control rats, respectively (n=5, P＞0.05). Immunohistochemistry identification indicated that immunological reaction of K(subscript V)1.2 channel protein was attenuated, but K(subscript V)1.5 channel protein was not altered. Positive staining intensity normalized by gray values of K(subscript V)1.2 channel were 173±13 and 131±11 in STZ rats and control rats, respectively (n=5, P＜0.05), but those of K(subscript V)1.5 channel were 139±16 and 141±12 in STZ rats and control rats, respectively (n=5, P＞0.05). These results suggested that impairment of cAMP-mediated endothelium independent vasodilation of rat small coronary artery by STZ-induced diabetes was resulted from decrease of mRNA and protein expressions of K(subscript V) channels, and which eventually leads to a reduced current from K(subscript V) channels.

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