Mechanism of cardiac dysfunction after myocardial contusion and the changes of intramyocardial calcium and myocardial ATPase in rabbits
Abstract：BACKGROUND:It is still unknown that whether cardiac dysfunction is related with intramyocardial calcium and myocardial ATPase except mycardial systolic pressure decreases induced by direct violent damages after myocardial contusion. OBJECTIVE:To explore the mechanic significance of intramyocardial calcium and myocardial ATPase in cardiac dysfunction after myocardial contusion(MC) in rabbits. DESIGN:A randomly case-control study. SETTING,MATERIALS AND INTERVENTIONS:The research was completed in Third Military Medical University.36 Sichuan healthy rabbits selected with either gender were allocated into before injury,2,4,8,12,and 24 hours after injury groups with 6 rabbits each.Cannula was inserted into left ventricule through right common carotid artery.The models of MC were established with BIM Ⅱ bio-impactor. MAIN OUTCOME MEASURES:Cardiac functions,free calcium content and the ATPase activity in myocardial tissue and cardiomyocytic mitochondria before injury 2,4,6,8,12 and 24 hours after injury. RESULTS:The function of contraction/diastolization of left ventricular was impaired.Indices represented left ventricular contraction function were left intraventricular end-systolic pressure(LVESP),the maximal rate of left ventricular pressure change(+ dp/dtmax),isovolumetric ventricular pressure(IP),and the maximal physiological velocity(Vmp),which returned to the level before MC in 4 to 12 hours after MC(P >0.05);main indices represented left ventricular diastolization function were descending time constant T of left intraventricular pressure during isovolumetric diastolization phase,left ventricular end-diastolic pressure(LVEDP),and the maximal rate of left intraventricular pressure changes(- dp/dtmax),which had significant differnce compared between before MC and 24 hour after MC(P< 0.05,P< 0.01). The average value of fluorescence of intramyocardial Ca2+ before MC was (2.26± 0.16),and began to increase to (2.63± 0.4) after 2 hours of MC (P >0.05),and hit its peak value of (3.56± 0.33) at 8 hour after MC (P< 0.01),which decreased since but still higher than that of before MC after 24 hours of MC(P< 0.05).2 hour after MC,ATPase in homogenate of myocardial tissue decreased with different degrees,thereinto,the activity of Ca2+-ATPase distinctly decreased after 4 hours of MC(P< 0.05); Ca2+-ATPase and Na+-K+-ATPase decreased to the lowest after 8 hours of MC(P< 0.05,P< 0.01).The values increased after 12 hours of MC and had no significance compared with that of before MC(P >0.05).The activity of Mg2+-ATPase decreased after MC compared with that of before MC,but with no significance(P >0.05).The ATPase in cardiomyocytic mitochondria decreased markedly after MC(P< 0.05) after 4 hours of MC and then increased and with no significance after 24 hours of MC(P >0.05).LVEDP and -dp/dtmax had a marked positive correlation with the changes of cardiomyocytic free calcium contents(r=0.792,0.753,P< 0.01,P< 0.05),and a marked negative correlation with the activity changes of myocardial Na+-K+-ATPase(r=- 0.674,- 0.691,P< 0.05),and a marked negative correlation with myocardial Ca2+-ATPase activity(r=- 0.613,- 0.642,P< 0.05),and a marked negative correlation with the activity changes of Na+-K+-ATPase in caridomyocytic mitochondria(r=- 0.622, - 0.616,P< 0.05). CONCLUSION:The cardiac functions are changed obviously after MC.The increase of the free calcium and the decrease of the activity of the ATPase in myocardial cells and cardiomyocytic mitochondria might contribute to cardiac dysfunction after MC.
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Publication Date：2004-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：3( 1160-1162 )