Effects of cyanide and deoxyglucose on Ca²⁺ signalling in macrovascular endothelial cells

1.. We have studied the effects of the metabolic inhibitors cyanide (CN) and deoxyglucose (DG) on the intracellular Ca²⁺ concentration ([Ca²⁺](i)) in macrovascular endothelial cells derived from human umbilical vein (EA cells). 2. CN^- and DG increased [Ca²⁺](i) in non-voltage clamped cells. This effect was dependent on extracellular Ca²⁺ concentration and membrane potential, indicating that CN^- induced a Ca²⁺ entry. 3. During expose to CN^- and/or DG, EA cells depolarise. This depolarisation is sometimes preceded by a small, but transient hyperpolarisation due to activation of a big - conductance K⁺ channels, BK(Ca) present in EA cells. However, in approximately 90% of the cells tested, the CN^- and/or DG induced elevation of [Ca²⁺](i) was insufficient to activate BK(Ca). 4. CN^- and/or DG enhanced BK(Ca) currents preactivated by an elevation of [Ca²⁺](i) via cell dialysis with 0.5 and 1 μM, respectively. Thus, metabolic inhibition sensitises BK(Ca). 5. The CN^- induced depolarisation of EA cells occurs by activating a current that reversed at positive membrane potentials. Substituting extracellular cations abolished the inward component of this current by NMDG, indicating that CN^- activated a non-selective cation channel, NSC. This current was reduced by extracellular Ca²⁺ and Mg²⁺ but is partially carried by Ca²⁺. 6. It is concluded that CN elevates [Ca²⁺](i) by activating Ca²⁺ permeable NSC channels. The properties of these channels are similar to those of the recently described trp3 channels expressed in endothelium.