Nitric oxide causes a cGMP-independent intracellular calcium rise in porcine endothelial cells-a paradox?
This study was undertaken to investigate the influence of exogenous NO on intracellular calcium levels of porcine aortic endothelial cell culture monolayers. Spontaneous NO liberating substances with different half-life periods (NOC-9 [10 micromol/L] approximately 1 min, SNAP [10 micromol/L] approximately 4 h), and an aqueous NO gas solution [130 nmol/L] were added onto the monolayers. All three solutions induced a rapid and similar calcium rise in the endothelial cells. NOC-9 as a rapidly NO releasing compound was selected to be investigated more thoroughly. The NOC-9 calcium rise is not dependent on the activation of the guanylate cyclase since preincubation with a specific guanylate cyclase inhibitor [ODQ, 10 micromol/L] did not alter the effect and a cGMP analogue [8-bromo-cGMP 10 micromol/L] did not significantly elevate calcium levels. The NOC-9 induced calcium rise could be completely blocked by removal of extracellular calcium and partly blocked by SKF 96365 [10 micromol/L], an unspecific inhibitor of the receptor operated calcium channels. Incubation with N-nitroarginine [100 micromol/L] slightly but significantly reduced basal calcium levels in the cell cultures. Therefore, we conclude that exogenous NO elevates [Ca(2+)](i) in cultured porcine aortic endothelial cells. This effect is not dependent on cGMP, and a calcium influx is involved. Moreover, constitutively formed endogenous NO seems to be necessary to maintain basal calcium levels.
Berkels
R
R
Institut fuer Pharmakologie, Universitaet zu Koeln, Koeln, 50931, Germany.
Suerhoff
S
S
Roesen
R
R
Klaus
W
W
D000818:Animals; D001011:Aorta; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D006834:Hydrazines / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007424:Intracellular Fluid / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009603:Nitroso Compounds / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D010396:Penicillamine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D013056:Spectrophotometry, Ultraviolet; D013552:Swine; D014226:Triazenes
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D006834:Hydrazines; D007093:Imidazoles; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D010069:Oxadiazoles; D011810:Quinoxalines; C110881:S-nitro-N-acetylpenicillamine; D014226:Triazenes; C099612:NOC 9; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D006162:Guanylate Cyclase; D010396:Penicillamine; D006152:Cyclic GMP; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium