Protection Of Propofol On Myocardial Mitochondrial Impairment Induced By Exogenous Ca～(2+) In Rat

Objective To observe the effects of propofol on myocardial mitochondrial impairment induced by exogenous Ca2+ in rat. Methods Thirty-five healthy Wistar rats (weight 217～234g) were killed by cervical dislocation. The hearts were quickly removed,enoughly cut and then homogenized about 10 stroke with a glass Dounce homogenizer. The isolation of rat heart mitochondria was performed by differential centrifugation. The protein concertration of mitochondrial suspension was determined by the Biuret method. The purity and activity of mitochondrial suspension was determined by enzymological method and lower activity was abstained. The experiments were divided into 5 groups at random (n=7). Mitochondria (1mg/2ml) were incubated in reaction buffer for 2 min and then were disposed differently. Group A was not disposed yet, group B was added CaCl2 (100nmol/mg prot) while group C～E were respectively added propofol of different concertration (25μM,50μM and 100μM) before CaCl2 (100nmol/mg prot) was added. Record absorptance value (A value) of the 0,4,8,12,16,20min. The magnitude of MPT was expressed by A value. Then the mitochondrial suspension was centrifuged at 13000g for 10min at 4â—‹C. The release of Cyt C were determined by western blot analysis. Results Determination of MPT: The results showed that A value of group B decreased significantly at 8 min compared with that at o min. The difference had statistically significance (p<0.05). It reveals that the mitochondria were injuried by Ca²⁺ and aggravated gradually (p<0.05 and p<0.01). Propofol of three concertration all significantly elevated the A value at every timepoint. Compared with group B, the difference had statistics significance (p<0.05). Compared group C,D and E with group A, the difference also had statistics significance (p<0.05) at 12,16 and 20min. A value was significantly elevated compared group D and E with group A(p<0.05). While at 16 and 20 min, 100μM propofol in group E significantly elevated the A value compared with 50μM propofol in group D (p<0.05). Determination of the release of Cyt C: Cyt C significantly released from the mitochondria in group B compared with that in group A (p<0.05). It respectively had statistically significant difference between group C,D,E and group A,B (p<0.05). 50μM propofol in group D and 100μM propofol in group E significantly inhibited the release of Cyt C. Compared with 25μM propofol in gronp C (p<0.05). No statistically significant differences were observed between group D and group E (p<0.05). Conclusions Exogenous Ca2+ could induce MPT and the release of Cyt C, thus injurying the structure and function of myocardial mitochondria. Intravenous anesthetics propofol can protect the myocardial mitochondria injuryed by Ca2+ through inhibiting the MPT and the release of Cyt C, as may be one of the main mechanisms by which propofol reduce myocardial apoptosis and play the role of myocardial protection.