Cytosolic calcium concentration is reduced by photolysis of a nitrosyl ruthenium complex in vascular smooth muscle cells.
The effect of the NO donors cis-[RuCl(bpy)(2)(NO)](PF(6)) (RUNOCL) and sodium nitroprusside (SNP) on the cytosolic Ca(2+) concentration ([Ca(2+)](c)) was studied in cells isolated from the rat aorta smooth muscle of cells isolated from the rat aorta smooth muscle. SNP is a metal nitrosyl complex made up of iron, cyanide groups, and a nitro moiety; the RUNOCL complex is made up of ruthenium and bipyridine ligands, with chloride and nitrosyl groups in the ruthenium axial positions. Rat aorta smooth muscle cells were loaded with fluo-3 acetoxymethyl ester (Fluo-3 AM) and imaged by a confocal scanning laser microscope excited with the 488 nm line of the argon ion laser. Fluorescence emission was measured at 510 nm. One of the NO donors, RUNOCL (100 micromol/L) or SNP (100 micromol/L), was then added to the cell chamber and the fluorescent intensity percentage (%IF) was measured after 240 s. RUNOCL reduced the %IF to 60.0+/-10.0% of the initial value. After treatment with the soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ) (10 micromol/L), the measurement of %IF was 81.0+/-5.0% (n=4). In the presence of tetraethylammonium (TEA) (1 mmol/L) the %IF was 79.0+/-6.4% (n=4). A combination of ODQ and TEA increased the %IF to 97.0+/-3.5% (n=4). As for SNP, it reduced the %IF to 81.4+/-4.7% (n=4), but this effect was inhibited by ODQ (%IF 94.0+/-3.6%; n=4) and TEA (%IF 88.0+/-2.1%; n=4). The combination of ODQ and TEA increased (%IF 92.0+/-2.8%; n=4). Taken together, these results indicate that both the new NO donor RUNOCL and SNP reduce [Ca(2+)](c). Our data also give evidence that soluble guanylyl cyclase and K(+) channels sensitive to TEA are involved in the mechanisms responsible for the reduction in [Ca(2+)](c) of the rat aorta smooth muscle cells.
Lunardi
C N
CN
Depto. de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, 14040-903 Ribeirão Preto, SP, Brazil.
Cacciari
A L
AL
Silva
R S
RS
Bendhack
L M
LM
D000818:Animals; D001011:Aorta / Q000033:anatomy & histology; D002118:Calcium / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry*; D008297:Male; D015394:Molecular Structure; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000378:metabolism*; D009599:Nitroprusside / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D010782:Photolysis; D051381:Rats; D017208:Rats, Wistar; D017975:Ruthenium Compounds / Q000737:chemistry / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D020030:Nitric Oxide Donors; D017975:Ruthenium Compounds; D014662:Vasoconstrictor Agents; D009599:Nitroprusside; D010656:Phenylephrine; D002118:Calcium