The nitric oxide donor cis‐[Ru(Cl)(bpy)2(NO)](PF6) induces rat aorta relaxation and Ca2+ reduction under visible light irradiation.

Abstract

The relaxant effect of the nitric oxide (NO) donors cis-[Ru(Cl)(bpy)2(NO)](PF6) (RUNOCL) and sodium nitroprusside (SNP) was investigated in the rat denuded aortic rings and on the cytosolic Ca2+concentration ([Ca2+]c) in aorta smooth muscle cells. RUNOCL and SNP induced relaxation in a concentration dependent way. RUNOCL was studied by photo-induction using a visible light emission source (3.4x1017 einstein s−1) system with excitation range up to ?? 300 nm to release NO from the complex. The maximum effect induced by RUNOCL was 101.16±3.74% and pD2 6.62±0.16, n=7 and SNP 99.39±4.37% and pD2 8.57±0.22, n=5. Cells loaded with Fluo-3AM were imaged by a confocal scanning laser microscope excited at 488 nm line of argon ion laser and the emission was measured at 510 nm. ([Ca2+]c was calculated in fluorescence intensities (IF) from control IF (100% phenylephrine 0.1μmol/L). RUNOCL (100 μmol/L) or SNP (100 μmol/L) was added to the chamber and the %IF was measured after 240 seconds in the absence or after incubation for 30 min with the given inhibitor. RUNOCL reduced ([Ca2+]c to 60.0±10.0%, n=4 and in presence of guanylyl cyclase inhibitor (10 μmol/L ODQ) IF was 81.0±5.0% and with K+channel blocker (1mmol/L TEA) IF was 79.0±6.43%. The combination of ODQ and TEA increased the IF (97.0±3.5%). SNP reduced IF to 81.4±4.7%, n=4 that was inhibited by ODQ (94.0±3.6%) and by TEA (88.0±2.1%). Combination of ODQ and TEA increased the IF (92.0±2.8%). In conclusion, RUNOCL and SNP reduce [Ca2+]c and this effect involves guanylyl cyclase and K+ channels sensitive to TEA. Supported by FAPESP and CNPq.