Pflugers Arch - Eur J Physiol (2002) 444:438–445 DOI 10.1007/s00424-002-0825-x Abstract We have studied the properties of a non-selec- tive cation current (NSC Ca ) in macrovascular endothelial cells derived from human umbilical vein (EA cells) that is activated by an increase of intracellular Ca 2+ concen- tration, [Ca 2+ ] i . Current–voltage relationships are linear and the kinetics of the current is time-independent. Current–[Ca 2+ ] i relationships were fitted to a Ca 2+ binding site model with a concentration for half-maximal activa- tion of 417±76 nM, a Hill coefficient of 2.3±0.8 and a maximum current of –23.9±2.7 pA/pF at –50 mV. The Ca 2+ -activated channel is more permeable to Na + than for Cs + (P Cs /P Na =0.58, n=7), but virtually impermeable to Ca 2+ . Current activation was transient if ATP was omitted from the pipette solution. The maximal currents at 300 and 500 nM [Ca 2+ ] i were smaller than in the absence of ATP, but were not significantly different at 2 μM. The intracellular Ca 2+ concentration for half-maxi- mal activation of the Ca 2+ -activated current was shifted to 811±12 nM in the absence of ATP. Substitution of ATP by the non-hydrolysable ATP analogue adenylylim- idodiphosphate (AMP-PNP) did not affect current acti- vation. Sodium nitroprusside (SNP) decreased NSC Ca in a concentration-dependent manner. The nitric oxide (NO) donors S-nitroso-N-acetylpenicillamine (SNAP) and 3-morpholinosydnonimine (SIN-1) also inhibited NSC Ca . In contrast, nitro-L-arginine (NLA), which inhibits all NO-synthases, potentiated NSC Ca , whereas superoxide dismutase (SOD), which inhibits the breakdown of NO, inhibited NSC Ca . It is concluded that the Ca 2+ -activated non-selective action channel in EA cells is modulated by the metabolic state of the cell and by NO. Keywords Intracellular calcium · Metabolic inhibition · Nitric oxide · Non-selective cation channels Introduction Many cellular functions of endothelial cells (EC) are controlled by intracellular Ca 2+ , such as the production and release of various vasoactive factors, e.g. nitric oxide (NO), prostaglandin I 2 (PGI 2 ), and factors involved in blood clotting, tissue factor pathway inhibitor (TFPI), von Willebrand factor (vWF), tissue plasminogen activator (tPA). In addition, Ca 2+ entry is also involved in control- ling intercellular permeability, EC proliferation and angiogenesis (for a review see [27]). The molecular identity and properties of the various pathways for Ca 2+ entry into ECs are still a matter of debate. They comprise agonist-activated non-selective Ca 2+ -permeable cation channels, cyclic-nucleotide-activated non-selective cation channels and store-operated Ca 2+ channels. Some of these channels are permeable to Ca 2+ while others depolarize the cell membrane and thereby reduce the driving force for Ca 2+ entry (for a review see [27, 35]). Various receptor-activated non-selective cation channels in EC have been described [9, 15]. Most of these channels are activated via signalling cascades involving activation of phospholipase β (PLCβ) and may belong to the super-TRP family, a family of six transmembrane helix channels of which several members are present in endothelium [8]. A non-selective, Ca 2+ -permeable cation channel activated by an increase in [Ca 2+ ] i has been described in endothelial cells, but its mechanism of acti- vation and modulation are not known. Interestingly, oxidant stress, which induces superoxide anions, activates a 28-pS cation channel, which is equally permeable to Na + and K + and also to Ca 2+ . Oxidized glutathione, a cytosolic product of oxidant metabolism, activates these channels, whereas reduced glutathione reverses activation [20, 21]. We show here that the Ca 2+ -activated channel in macrovascular ECs derived from human umbilical vein S.H. Suh · H. Watanabe · G. Droogmans · B. Nilius ( ✉ ) Katholieke Universiteit Leuven, Laboratorium voor Fysiologie, Campus Gasthuisberg, 3000 Leuven, Belgium e-mail: bernd.nilius@med.kuleuven.ac.be Tel.: +32-16-345937, Fax: +32-16-345991 S.H. Suh Department of Physiology, College of Medicine, EWHA Women’s University, 911–1 Mok-dong, Yang Chun Gu, Seoul, Korea ORIGINAL ARTICLE Suk H. Suh · Hiroyuki Watanabe · Guy Droogmans Bernd Nilius ATP and nitric oxide modulate a Ca 2+ -activated non-selective cation current in macrovascular endothelial cells Received: 8 January 2002 / Accepted: 15 February 2002 / Published online: 29 March 2002 © Springer-Verlag 2002