Ischaemic preconditioning alters the energy metabolism and protects the ischaemic myocardium in a stepwise fashion.
OBJECTIVE
Recently it was suggested that ischaemic preconditioning (IP) protects the myocardium in a graded pattern as assessed by myocardial infarct size estimation. Using tissue biopsies we investigated the impact of the proposed graded pattern of protection on myocardial energy state in an open-chest porcine model of IP with either one (1xIP) or four (4xIP) episodes of preconditioning. Furthermore, we evaluated the relationship between interstitial energy-related metabolite levels obtained by the microdialysis technique and the degree of subsequent ischaemic insult.


RESULTS
During the long ischaemia the difference between pre-ischaemic and post-ischaemic total adenylate pools and the sum of adenylate breakdown products (adenosine, inosine and hypoxanthine) as well as tissue lactate levels appeared as follows: non-IP > 1xIP > 4xIP (P < 0.05). Moreover interstitial peak levels of lactate, hypoxanthine and taurine displayed a graded pattern analogous to the development of ischaemic damage, where non-IP > 1xIP > 4xIP.


CONCLUSIONS
We present for the first time concordant energy metabolic and morphometric data in support of IP being a stepwise phenomenon for protection of the ischaemic myocardium. Furthermore, IP resulted in proportionally higher levels of hypoxanthine (relative to inosine) in the ischaemic myocardium, suggesting a different handling of adenine nucleotide breakdown products in the IP myocardium.
Kavianipour
M
M
Department of Public Health and Clinical Medicine, Norrland University Hospital, Umeå, Sweden.
Ronquist
G
G
Wikström
G
G
Waldenström
A
A
D000244:Adenosine Diphosphate / Q000032:analysis / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000032:analysis / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000032:analysis / Q000378:metabolism; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D007773:Lactates / Q000032:analysis; D008297:Male; D017551:Microdialysis / Q000379:methods; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology
D007773:Lactates; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate