Effect Of Microenvironment On The Incidence Of Cardiovascular Disease

The Aim of this study was to explore the effects of micro-environmental on the cardiovascular diseases, to identify the location that O₂^●- generates in diabetes conditions, to observe the influence of O₂^●- on function of Kv channels, and to reveal the effects of micro-environment changes (ischemia, hypoxia, and pH alteration) and external chemicals on I_to in cardiac cells.This study established the diabetic animal model by STZ, a toxic chemical and diabetic-mimic cell culture model; The location where O₂^●- generated in small rat coronary artery in diabetic micro-environment was studied by the fluorescence imaging technique and immunohistochemical technique; The contraction and relaxation function of the coronary artery and effects of isoprenaline, forskolin, and 4-AP on the coronary artery in hyperglycemic micro-environment were investigated with the small artery perfusion technique in vitro; Functional changes of Kv channel were measured with patch clamp technique and Western-blot technique in hyperglycemic micro-environment in coronary artery smooth muscles; Furthermore, the electrophysiological technique was used to study effects of micro-environment changes (ischemia, hypoxia and pH alteration) and external chemicals on I_to in canine ventricular myocytes, in order to find out the chemicals which can keep the homeostasis of the micro-environment.The experiments showed that streptozotocin (STZ) could induce rat hyperglycemia, with the weight of 191²20g and the 87.5% rate of success under the duration of 8h sunshine; The quantity of O₂^●- was increased in coronary artery endothelial tissue,adventitia and smooth muscle tissue in diabetic rat; However, the quantity of O₂^●- was increased only in endothelial tissue after smooth muscle cells from diabetic rat coronary artery was cultured under hyperglycemic condition for 24 hours; Additionally, there was no significant increase of the quantity of O₂^●- in cultured smooth muscle cells under hyperglycemic conditions; The results indicated that O₂^●- only was generated in endothelial tissues under short-term hyperglycemic micro-environment. The study demonstrated that hyperglycemic micro-environment inhibited Kv channels and decreased the expression of Kv1.2 and Kv1.5 channel protein, which resulted in the inhibition of vasorelaxation by cellular membrane depolarization. The effects were not related to K+, KATP channels and Ca2+ channels under hyperglycemic micro-environment, but involved in the inhibition of cAMP signaling system. Oxygen free radical scavenger significantly improved the coronary artery vasorelaxation function in diabetic rats, and played an important role in regulating the smooth vascular contraction and relaxation of coronary artery.The changes of micro-environment had significant effects on I_to which was closely associated with myocardial ischemia, arrhythmia, and heart dysfunction. The micro-environment alteration induced by cardio-toxin, aconitine and ouabain resulted in abnormality of I_to in single cardiomyocyte. RP58866 and RP62719 had significant effects on I_to in low concentrations (1, 10 mol·L-1), which showed higher potency than other analogs. The results indicated that the excessive decrease of I_to by cardio-protective agents may be a risk factor for the development of arrhythmias. Cardio-protective agents, such as artemisinin, cyclovirobuxine D, and extracts of the Cordyceps sinensis exerted slight effects on I_to in ventricular myocytes. These suggested that I_to was regulated by these agents in ventricular myocytes when the micro-environment changed in the heart, which avoided the negative effects induced by excessive inhibition of I_to. Matrine had no obvious influence on I_to, but it prevented effects of aconitine on I_to. It is indicated that matrine will be an ideal substance modulating the micro-environment and maintaining the homeostasis. So an ideal micro-environment modulated drugs should clean oxygen free radical, regulate Kv channels and not excessively inhibit or increase I_to.