Irrelevance of BK_(Ca) Channel Expression to VSMCs Phenotype under Shear Stress

摘要

Large conductance Ca~(2+)-activated K~+ (BKc.) channel exhibits a phenotype-dependent expression on vascular smooth muscle cells (VSMCs), which it prefers to contractile phenotype. Meanwhile, shear stress definitely influenced VSMCs proliferation and contraction. Thereby, a hypothesis was raised, would do shear stress change the BK_(Ca) expression and correlate with VSMC phenotype? To investigate it, VSMCs were exposed to shear stress in a parallel-plate flow chamber with 12 dynes/cm~2 for 12 h. Subsequently, the effect of shear stress on VSMC proliferation, BK_(Ca) channel expression and contractile phenotype marker, a-smooth muscle cell actin (a-SMA) and smooth muscle myosin heavy chain (SM-MHC), was determined by immunofluorescence microscopy, flow cytometery as well as reverse transcription-polymerase chain reaction (RT-PCR), respectively. Data showed that shear stress enhanced the expression of BK_(Ca) channel while inhibiting VSMC proliferation. Paralleled to those phenomena, the expression of both a-SMA and SM-MHC were decreased significantly. These results demonstrated that upregulation of BK_(Ca) channel was irrelevant to the maintenance VSMC of contractile phenotype under shear stress. This finding provides a new insight into understanding the correlation of BK_(Ca) channel and VSMC phenotype.