Summary
Nitric oxide (NO) is a potent vasoactive gasotransmitter which plays a key role in physiological and pathological processes related to vascular tone.The present investigation includes two sets of experiments. In the first experimental set, the study was concerned with the role of endothelial derived relaxation factors, chloride channels and potassium channels in nitric oxide induced relaxation in thoracic aorta in male experimental rats.
The maximum relaxation provoked by SNP significantly blocked when aortic rings were incubated in free Cl–solution IC50.The results implied that chloride ion is crucial for relaxation induced by SNP.
The IC50 and PIC50 for the relaxant response to SNP following sustained contraction were significantly higher in rings pre-incubated with L-NAME, while significantly decreased when aortic rings pretreated with Indomethacin and Clotrimazole.
To identify the types of Cl–channels involved in SNP-induced relaxation, aortic rings were preincubated for 20 minutes with 9 AC (1mM), BUM (10-5), DIDS (1mM) and Niflumic acid (1mM). The maximum vasorelaxation induced by SNP significantly blocked by the presence of 9AC, BUM and DIDS, whilst not changed by the presence of Niflumicacid, while pre-incubation of aortic rings with individual of BUM and DIDS significantly reduced PIC50 caused by SNP. In contrast, pretreatment of aortic rings with individual of 9AC and Niflumic acid significantly enhanced PIC50.
SNP-induced relaxations were significantly inhibited only when aortic rings pre-incubated with GLIB, while did not change when aortic rings were preincubated with TEA and BaCl2. On the other hand, PIC50 of aortic rings pre-incubated with TEA, GLIB and BaCl2 significantly inhibited SNP relaxation when compared to control rings.
SNP induced relaxation were not affected by combination of BUM with either (L-NAME, Clotrimazole, TEA and BaCl2), while significant blocking of SNP recorded in pre-incubation with BUM and indomethacine .
On the other hand PIC50 of aortic ring pre-incubated with the combination of BUM and L-NAME significantly increased as compared to control , where as significant inhibition in PIC50 were identified in all the other four combinations including BUM+ Indomethacine, BUM+ TEA and BUM +BaCl2.
While the second set of experiments studied the effects of endothelial dysfunction induced by high glucose solution on the molecular pathway of nitric oxide induced aortic relaxation. Incubation of aortic rings with high (4%) glucose significantly blocked relaxation induced by SNP.
The PIC50 for the relaxant response to SNP following sustained contraction were significantly higher in rings preincubated with Indomethacin and L-NAME, while significantly decreased when aortic rings pretreated with Clotrimazole.
Statistical significant induction of SNP was recorded via pre-incubation of BUM which indicates the negative participation of CCl channels in SNP-induced aortic relaxation. Furthermore the PIC50 for SNP-induced relaxation pre-incubated with BUM was significantly higher than SNP endothelial dysfunction.
The maximum vasorelaxation induced by SNP was significantly reduced by blocking of KCa channel. The PIC50 for pre-incubation of TEA was significantly higher than control aortic rings.While SNP significantly induced relaxation by pre-incubated BaCl2in endothelial dysfunction aortic rings.
To confirm the involvement of these K+channels in high glucose-induced endothelial dysfunction vasodilation, we tested the specific KCa and KIR channels blockers.Vasodilation in response to SNP in high glucose solution was completely abolished when only one of these channels was blocked.
The effect of BUM and L-NAME combination on relaxation caused by SNP showed that the pre-incubation of Cl– channel and NOS inhibitors together did not produce any significant alteration on SNP relaxation of NE induced contraction in endothelial dysfunction aortic rings.
Posted: 23/05/2016 (Salahaddin University- Erbil, College of Science)