| Objective:to establish a rat exercise-induced cardiac hypertrophy model, to observe changes of expression of Gaq, PKC-α, Raf-1, MEK1, MEK2, ERK1, ERK2in myocardium of exercise-induced cardiac hypertrophy rats, to study the role and its mechanism of signal channel of "PKC/MAPK" in exercise-induced cardiac hypertrophy, to provide partial theoretical basis for revealing the mechanism of exercise-induced cardiac hypertrophy.Methods:1.Group rats:32female SD rats, weighing180g-200g, were randomly assigned into2groups:normal control group(SC, n=16) and cardiac hypertrophy model group (SE, n=16).2. Establish a model of animals with exercise-induced cardiac hypertrophy:exercise-induced cardiac hypertrophy animal model was established based on modified Reznick model and Tiago Fernandes model. The rats swam load free for8weeks:measured the weight of rat and monitored the blood pressure weekly during the experiment period.3. After8weeks of swimming, remove the rat heart and calculate the cardiac index, left ventricular coefficient; observe the changes of myocardial tissue morphology under the HE-stained microscope. Measure the expression of α-actin, ANP, α-MHC and β-MHC alpha mRNA in rats’ myocardium using the real-time fluorescence quantitative PCR method, calculate α/β-MHC, evaluate the success of the establishment of the exercise-induced cardiac hypertrophy model.4. After assuring the establishment of exercise-induced cardiac hypertrophy rat model, use real-time fluorescence quantitative PCR method to determine the expression of Gaq, PKC-a, Raf-1, MEK1, MEK2, ERK1, ERK2mRNA in rats’ myocardial tissue.Results:1. the weight of two rat groups both increase after8weeks of swimming, SE rats weighed significantly less than SC control group rats (P<0.01), but the heart weight of SE group rats significantly gained compared to the SC group (P<0.01); the heart coefficient of SE group rats was significantly larger than the SC rats (P<0.05); the left heart coefficient of the SE exercise group rats was significantly larger than the SC control group (P<0.01). Observe tissue slice under light microscope that myocardial fibers have uniform color, normal structure, stumpy shape, connected network, and the nucleus appear oval-shape, uniform size distribution, clearly visible myocardial stripes. The cardiomyocytes diameter of SE exercise group expanse dramatically more than the SC group (P<0.05), which demonstrated the success of the establishment of the exercise-induced cardiac hypertrophy model. The blood pressure in SE rats in exercise group declined more than that of SC control group but there was no significant difference (P>0.05), the expression of α-actin, α/β-MHC mRNA S in SE group decresed more than that of SC control group but there was no significant difference (P>0.05), and the expression of ANP mRNA in SE exercise group rose more than that of SC control group but there was no significant difference (P>0.05), which indicated that rat’s heart had no pathological changes thus this exercise-induced cardiac hypertrophy is a physiological cardiac hypertrophy.2. After the8-week experiment, the expression of GaqmRNA in SE exercise group went up more than that of SC control group but there was no noticeable difference (P>0.05), which indicated that8-week exercise has little effect on the expression of Gαq mRNA in rats ’myocardium.3, After the8-week experiment, the expression of Raf-1, MEK1, MEK2mRNA GaqmRNA in SE exercise group all increased significantly compared to the SC control group (P<0.01), which indicated that8-week exercise could unregulated the expression of Raf-1, MEK1, MEK2and mRNA in rats’myocardium4, After the8-week experiment, the expression of PKC-α, ERK1, ERK2mRNA in SE exercise group all increased significantly compared to the SC control group (P<0.05), which indicated that8-week exercise could unregulated the expression of PKC-α, ERK1, ERK2, mRNA in rats ’myocardium.Conclusion:1, this experiment has successfully established an exercise-induced cardiac hypertrophy model.2, This experiment result demonstrated that exercise stimulus the elevation in the expression level of PKC gene in rats ’myocardium, thus activated the MAPK signal channel, exercise-induced mechanical stress stimulation can activate partial molecules that connected by the cell membrane, PKC (protein kinase C) activity changes, the activation of PKC may activate Raf Ser/Thr protein kinase. The three isozymes, α-Raf, β-Raf and Raf-1of the active Raf could phosphorylate and activate the corresponding downstream MEK. Raf-1could identify and activate MEK1and MEK2, ERK1and ERK2were the corresponding downstream substrates of MEK1and MEK2, ERK1and ERK2displaced from cytoplasm to nucleus after being phosphorylated and activated, then ultimately caused a series of cytoplasm, nuclear regulatory proteins involved in the process of myocardial hypertrophy when, may be the molecular mechanism of exercise-induced myocardial hypertrophy.3, This experiment result show that, during the generation and development process of the exercise-induced cardiac hypertrophy, Gaq on had not played a leading role in the activation of the PKC/MAPK signal channel, therefore it can be concluded that the signal channel between Gaq and PKC/MAPK in the exercise-induced cardiac hypertrophy model is not simply a upstream and downstream relationship. The Effect of Gaq in exercise-induced cardiac hypertrophy is completely different from that in pathological cardiac hypertrophy, which sepcific mechanism requires futher experimental verfication.(P<0.01), but the heart weight of SE group rats significantly gained compared to the SC group (P<0.01); the heart coefficient of SE group rats was significantly larger than the SC rats (P<0.05); the left heart coefficient of the SE exercise group rats was significantly larger than the SC control group (P<0.01). Observe tissue slice under light microscope that myocardial fibers have uniform color, normal structure, stumpy shape, connected network, and the nucleus appear oval-shape, uniform size distribution, clearly visible myocardial stripes. The cardiomyocytes diameter of SE exercise group expansed dramtically more than the SC group (P<0.05), which demonstrated the success of the establishment of the exercise-induced cardiac hypertrophy model. The blood pressure in SE rats in exercise group declined more than that of SC control group but there was no significant difference (P>0.05), the expression of α-actin, α/β-MHC mRNA S in SE group decresed more than that of SC control group but there was no significant difference (P>0.05), and the expression of ANP mRNA in SE exercise group rose more than that of SC control group but there was no significant difference (P>0.05), which indicated that rat’s heart had no pathological changes thus this exercise-induced cardiac hypertrophy is a physiological cardiac hypertrophy.2. After the8-week experiment, the expression of GaqmRNA in SE exercise group went up more than that of SC control group but there was no noticeably difference (P>0.05), which indicated that8-week exercise has little effect on the expression of Gaq mRNA in rats ’myocardium. 3, After the8-week experiment, the expression of Raf-1, MEK1, MEK2mRNA Gaq mRNA in SE exercise group all increased significantly compared to the SC control group (P<0.01), which indicated that8-week exercise could upregualte the expression of Raf-1, MEK1, MEK2and mRNA in rats’myocardium4, After the8-week experiment, the expression of PKC-α, ERK1, ERK2mRNA in SE exercise group all increased significantly compared to the SC control group (P<0.05), which indicated that8-week exercise could upregualte the expression of PKC-α, ERK1, ERK2, mRNA in rats ’myocardium.Conclusion:1, This experiment has successfully established an exercise-induced cardiac hypertrophy model.2, This experiment result demonstrated that exercise stimulus the elevation in the expression level of PKC gene in rats ’myocardium, thus activated the MAPK signal channel, exercise-induced mechanical stress stimulation can activate partial molecules that connected by the cell membrane, PKC (protein kinase C) activity changes, then ultimately caused a series of cytoplasm, nuclear regulatory proteins involved in the process of myocardial hypertrophy when, may be the molecular mechanism of exercise-induced myocardial hypertrophy.3, This experiment result show that, during the generation and development process of the exercise-induced cardiac hypertrophy, Gaq on had not played a leading role in the activation of the PKC/MAPK signal channel, therefore it can be concluded that the signal channel between Gaq and PKC/MAPK in the exercise-induced cardiac hypertrophy model is not simply a upstream and downstream relationship. The Effect of Gaq in exercise-induced cardiac hypertrophy is completely different from that in pathological cardiac hypertrophy, which sepcific mechanism requires futher experimental verfication. |
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