Flow-activated Na(+)and K(+)Current in cardiac microvascular endothelial cells

The patch-clamp technique was used to investigate the electrical response of cardiac microvascular endothelial cells to fluid stream applied through a microtube. The fluid stream induced a membrane current whose amplitude was dependent on flow rate. The I-V relationship of the flow-activated current showed a strong inward rectification and a reversal potential close to +30 mV, which gave a P(Na)/P(k)=3.47. The inward and outward components of the current nearly disappeared when extracellular Na(+)and internal K(+), respectively, were replaced by NMDG(+). Finally, the flow-activated current was fully blocked by 50 microM Gd(3+)and La(3+). These results show that cardiac microvascular endothelial cells respond to mechanical stimulation associated with flow by increasing their permeability to Na(+)and K(+). This mechanism is suggested to contribute to ionic homeostasis at high heart rates and during post-ischaemic reperfusion.