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 PNa/Pk=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 μ Gd3+and La3+. 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.