Age-related difference in myocardial function and inflammation in a rat model of myocardial ischemia-reperfusion.
OBJECTIVE
Aging is associated with a reduced tolerance to myocardial ischemia reperfusion injury when compared to the young adult. However, there is very little information in the literature regarding age-related changes in myocardial function and inflammation during myocardial ischemia-reperfusion (MI/R) in vivo.


METHODS
We examined age-related differences in myocyte apoptosis and the inflammatory response in a rat model of myocardial ischemia-reperfusion (MI/R). The aged (19 months) and young (4 months) male F344 BN rats were subjected to 30 min of myocardial ischemia by ligating the left main coronary artery, followed by release of the ligature and 4 h of reperfusion. Four experimental groups, e.g. young sham control, aged sham control, young rats subjected to MI/R, and aged rats subjected to MI/R, were studied.


RESULTS
MI/R induced a 78% increase in circulating leukocytes and a 30% increase in superoxide generation in the ischemic region of the heart of young rats, when compared to aged rats. Moreover, the arrhythmia scores were higher in young rats than in aged rats (P=0.058) following MI/R. There was no difference in hemodynamics between young sham and aged sham rats. However, the cardiac index was decreased by 34% at 3 h of reperfusion and by 33% at 4 h of reperfusion in aged rats, when compared to young rats following MI/R. Furthermore, stroke volume index was decreased by 54, 56, and 65% at 2, 3, and 4 h of reperfusion in aged rats, respectively, when compared that of young rats subjected to MI/R. There was an enhanced myocyte apoptosis, as indicated by ELISA and TUNEL staining in the myocardium of aged rats compared to young rats following MI/R. Interestingly, RT-PCR analysis indicated that MI/R significantly increased the ratio of Bax mRNA to Bcl-2 mRNA in aged rats compared to that of young rats (3.51 vs. 0.74).


CONCLUSIONS
MI/R is associated with an increase in circulating leukocytes and generation of superoxide in the peri-ischemic areas of the heart of young rats, compared to aged rats. However, MI/R induces a significant decrease in cardiac index and stroke volume index in aged rats, when compared to young rats following MI/R. Furthermore, aged rats exhibit an increase in the ratio of Bax mRNA to Bcl-2 mRNA and cardiomyocyte apoptosis following MI/R, which may explain, at least in part, the enhanced myocardial dysfunction.
Liu
Peitan
P
Department of Cell Biology, School of Osteopathic Medicine, University of Medicine and Dentistry of New Jersey, 2 Medical Center Drive, Stratford, NJ 08084, USA. liupe@umdnj.edu
Xu
Baohuan
B
Cavalieri
Thomas A
TA
Hock
Carl E
CE
D000375:Aging / Q000502:physiology*; D000818:Animals; D017209:Apoptosis; D001145:Arrhythmias, Cardiac / Q000209:etiology; D001794:Blood Pressure; D002302:Cardiac Output; D004195:Disease Models, Animal; D015870:Gene Expression; D006321:Heart / Q000503:physiopathology*; D007958:Leukocyte Count; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000150:complications / Q000503:physiopathology*; D032383:Myocytes, Cardiac / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011916:Rats, Inbred F344; D013318:Stroke Volume; D013481:Superoxides / Q000378:metabolism; D014655:Vascular Resistance; D051028:bcl-2-Associated X Protein
C494828:Bax protein, rat; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; D013481:Superoxides