| Ischemic heart disease is caused by coronal blood circulation changes andinduces the imbalance of myocardial supply and demand. its most commonpathogenesis is the straightening and obstruction of the coronary arteries fromatherosclerosis. Whether in developed countries or in developing countries,IHD is a deadly and deforming disease .so widely epidemic that it imperils thewhole of humankind's health. The therapeutic arsenal that is currently availableto physicians in combating IHD targets is deficient in direct cardio protectiveagents. A safe and effective new therapy that shows the progression ofmyocardial ischemic injury and protects the myocardial cell would therefore beexpected to synergies with existing therapies and provide considerable benefit. Rb1,a monomer of panaxadiol saponins,has been proved that it candecrease the heart rate, myocardial oxygen consumption, coronary arterialresistance. Rb1 could ameliorate the index of hemodynamics, decrease theraised myocardial enzyme, the positive percent of cardiocytes apoptosis andreduce the infarction area. All of this we stated above showed that Rb1 have theeffect of protect the cardiocytes. In order to investigate the direct function ofRb1 on ischemic cardiocytes and to provide theoretical reason for the clinical,we obtained single active ca2+ tolerance guinea pig ventricular myocytes byacute enzymatic dissociation. L-type calcium channel current (IL-ca), adenosinetriphosphate-sensitive potassium channel current (IKATP) and action potential wererecorded using the whole cell patch-clamp technique in ischemic cardiocytes.1. Isolation of ca2+ tolerant cardiocytesHearts were firstly perfused by the Langendorff perfusion apparatus withnormal Tyrode's solution, then with Ca2+ free Tyrode's solution andsubsequently with enzyme solution containing collagenase 0.16-0.2 g/L. All thesolutions were saturated with oxygen and the perfusion temperature was kept at37℃. Finally hearts were washed by Ca2+ free Tyrode's solution, after whichthe ventricle were minced into small pieces in KB solution, dispersed andfiltered. The isolated cardiocytes were stored in KB solution at roomtemperature for 1h before patch clamp experiments. Results: When all thefactors such as water, enzyme, Ca2+, pH, and oxygen were well controlled, thewell constructed and rod-like cardiac myocytes with a yielding rate of 30 %-50% came out.2. Effect of Rb1 on the action potential in guinea pig ventricular myocytes Action potential (AP) curve was recorded by current clamp technique. APwas elicited by a series of depolarizing pulse (5mS range, 0.5-1.0nA). Werecorded action potential amplitude (APA), resting potential (RP), actionpotential duration 50% (APD50), action potential duration 90% (APD90). Rb1can significantly abbreviate APD50 from 381.48 ±28.23mS to 291.72 ±22.6mS,APD90 from 398.64±26.77mS to 310.21±20.38mS in normalcardiocytes, Rb1 can significantly abbreviate APD50 from 212.42±15.32mS to148.35±12.56mS, APD90 from 228.6±11.34mS to 164.47±10.25mS inischemic cardiocytes. Rb1 have no effect on APA, RP.3. Effect of Rb1 on the L-type calcium channel current in ischemic guinea pigventricular myocytes. Standard whole cell IL-ca was recorded by patch clamp technique. IL-Ca waselicited by a series of depolarizing pulse (300mS range from –50mV to +60mV,...
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