| IntroductionBased on Murry's principle, investigators began to study non -traumatic or mini - traumatic precondition in order to extent the application of ischemic precondition( IP) . Non - traumatic and mini - traumatic precondition include anoxic precondition, drug precondition [eg. norepinephrine( NE) , adenosine( Ado) ] and so on. Recently some investigators used repetitive transient thigh ischemic precondition (TTIP) mimic the protective effect of IP and got desired results.Protective effect of IP is common to different kinds of animals and human, and easy to induce. Its believed that there was an universal mechanism mediated protection of IP. Investigators have proved that protein kinase C ( PKC ) played a central role on heart protection of IP in rabbits, rats, canines and other animals, even in human.After cadiac arrest, the key to successful cardio - pulmonary resuscitation ( CPR ) is global ischemia - reperfusion ( I/R ) . Whether precondition can increase the rate of successful CPR, improve life quality is worthy discussing. There is no report about the action of precondition on CPR.We performed asphyxia cardiac arrest and resuscitation ( ACAR) in rats to appraise the effect of precondition on CPR and briefly discussed its mechanisms.Materials and Methods1. Experimental preparation; Healthy male class II Wistar rats weighed 230 - 300g were anesthetized with sodium pentobarbital (45mg/kg) , intubated, and placed on a animal respirator (tidal volume lOml/kg, respiratory rate 807min). EGG changes were monitored continuously. Left jugular vein was performed for drug infusion and administered heparin 500u immediately. A Catheter was placed in left ventricle ( LV) through right common artery to obtain left ventricular pressure ( LVP).2. Grouping: (1)Control group ( C ): ACAR: Tracheal cannula was shut at end - expiration, rats were given artificial ventilation, chest compression 180 - 2207min and iv adnephrine 0. 02mg/kg when heart arrested ( showed as the cardiac functional curve be a line). ECG and cardiac function were used to determine the recovery of auto-circulation. (2)TTIP group (IP) : Left thigh root was ligated by a rubber line to stop the blood flow for lOmin, then loosed it. 10min later, performed ACAR. (3)NE or Ado precondition group I (NEPCI/Adol) ; A NE infusion of 1. 6ug( BW<250g) - 2. 0ug( BW >250g) or Ado infusion of 2 - 3umoL/kg. min was given for 5min. 10min later, performed ACAR. (4)NE or Ado precondition group II ( NEPCII/AdoII) : In addition to ACAR, iv NE 0. 2 -0. 3ug/kg or Ado 2 - 3umol/kg. min at beginning of CPR until autocirculation recovered or total dosage reached 1.6 -2.0ug (NE) or 10 - 15umol/kg( Ado).3. Measurements:(1)Rate of successful CPR: Successful CPR refers to recovery of autocirculation ( ECG shows normal QRS, cardiac functional curve has periodical changes, heart beats are easily palpa-ble and cyanosis is reduced significantly) and maintained for 30min. Data were reported as the percentage of the number of successful CPR rats to the number of total rats of each group ( % ). (2)Time of recovery of autocirculation: The time from beginning of CPR to autocirculation occuring. Data were reported as actual measurements ( s ) /Time of death(s) x 100%. (3)LV function; A catheter was placed in LV , connected with a pressure transmitter which transmits signals to a computer. By PcLab software, we measured LVDP: LV developed pressure ( mmHg) , + dp/dtmax: maximum velocity of elevated LVP in systol(mmHg/s) , - dp/dtmax: maximum velocity of descended LVP in diastol ( mmHg/s). Data were reported as actual measurements ( s)/ measurements of pre - precodition( s) x 100% . (4)Ultrastructure and PKC detection in heart tissue; Myocardial biopsy samples were taken from successful CPR rats at CPR 30min. Ultrathin sections of cardiac apex were examined with electron microscopy. PKC was detected by immunohistochemistry ( SABC ) , paraffine semisections were heated, anti - PKC sera was 1-75 dilution, color was developed with DAB. PKC loca...
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