ATP and nitric oxide modulate a Ca(2+)-activated non-selective cation current in macrovascular endothelial cells.
We have studied the properties of a non-selective 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+) concentration, [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 activation 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 microM. The intracellular Ca(2+) concentration for half-maximal 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 adenylylimidodiphosphate (AMP-PNP) did not affect current activation. 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.
Katholieke Universiteit Leuven, Laboratorium voor Fysiologie, Campus Gasthuisberg, 3000 Leuven, Belgium.
Suk H
SH
Suh
Hiroyuki
H
Watanabe
Guy
G
Droogmans
Bernd
B
Nilius
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002412:Cations / Q000378:metabolism; D002460:Cell Line; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014471:Umbilical Veins / Q000166:cytology
D002412:Cations; D007473:Ion Channels; D020030:Nitric Oxide Donors; C110881:S-nitro-N-acetylpenicillamine; D000266:Adenylyl Imidodiphosphate; D009569:Nitric Oxide; C002385:linsidomine; D000255:Adenosine Triphosphate; D008981:Molsidomine; D010396:Penicillamine; D002118:Calcium