| Background: Ischemic cerebrolvascular diseases are common diseases. The researches on the neuro-protective effect against ischemia-reperfusion(I/R) have been studied intensively in recent years. However, rather few studies have been done on the mechanisms of the injury on cerebral blood vessels. The "no-flow" after I/R, that no blood flow could be restored in the blocked vessels or the following distal vessels after thrombolysis, suggests the disorders exist in the cerebral blood vessel after I/R. As to cerebral vessels, activation of ATP-sensitive and calcium-activated potassium channels appears to play a major role in relaxation of cerebral arteries. But little is known about the role of the openers of these two channels in I/R. In this study, using hypoxia/reoxygenation(H/R) to mimic I/R injury, we examined the hypothesis that pretreatment with pinacidil and NS1619, specific openers of ATP-sensitive and calcium-activated potassium channels respectively, protects rabbit basilar artery from following H/R injury. Furthermore, we discussed whether the activation of ATP-sensitive and calcium-activated potassium channels of cerebral vessels contributes to protect cerebral artery against I/R.Objective : To identify the hypothesis that pretreatment with pinacidil and NS1619, specific openers of KATP and Kca respectively, protects rabbit basilar artery from following hypoxia/reoxygenation injury. Materials and Methods:Animals: New Zealand White rabbits of either sex and weighing 2.5 to 3.0 kg were used.Methods 1.Organ-chamber technique rabbit basilar artery rings were isolated and allocated in 4 groups: control (95 % O2 +5%CO2) , H/R injury: equilibrated for 90 min (95 % O2 +5%CO2), then changed to 30-minute hypoxia (95 % N2+5%CO2), followed by 30-minute reoxygenation (95 % O2 +5%CO2), pinacidil-pretreatment and NS1619-pretreatment: pinacidil (10 u mol/L) and NS1619(10 u mol/L) were added into the organ chamber 20 minutes prior to the H/R respectively. The rings were further divided into contraction group (n=6 in each group) and relaxation group(n=6 in each group). In contraction group, cumulative concentration-contraction curves were established for U46619, a stable thromboxane A2 analogue. In relaxation group, when the contraction to 0.1 u mol/L u46619 reached a stable plateau, cumulative concentration-relaxation curves to ACh and SNP were established respectively. The relaxation was expressed as percentage of the reduced contraction force induced by 0.1 u mol/L U46619 (The concentration of drugs are expressed as final bath concentration).2.Endothelial cell and smooth muscle viability test rabbit basilar artery rings were isolated and allocated in 4 groups(as previously described): control, H/R injury, pinacidil-pretreatment and NS1619-pretreatment. Each group was incubated with propidium iodide(7.5uM) for 5 min. Propidium iodide, a DNA fluorescent probe, is excluded from live but not dead cells. The stained vessel rings were rinsed, cut longitudinally and immediately mounted on microscope slides. The slides were viewed with a 20 x objective of ZEISS LSMS10 Axiovert 100M laser scanning confocal imaging system. Four areas of each vessel ring were randomly selected for observation.Results: â‘ Vascular responses to U46619 were significantly higher after H/R injury, however, SNP-induced vasorelaxation was not affected and ACh-induced vasorelaxation was significantly attenuated by H/R injury as compared with control; â‘¡ Pretreatment with pinacidil and NS1619 respectively prevented the H/R induced decreasement of ACh responsiveness and increasement of U46619 responsiveness of the rabbit basilar artery; â‘¢ There was no evidence of propidium iodide staining of smooth muscle cells in any of the optical sections in any of the four groups; The number of dead endothelial cells significantly increased after H/R. There was no significant difference in the number of dead endothelial cells between control, pinacidil-pretreatment and NS1619-pretreatment ; Thenumber of dead endothelial cells in...
|
PDF Full Text Request