© 1998 by European Society of Cardiology
Copyright © 1998, European Society of Cardiology
Lipid peroxidation, arachidonic acid and products of the lipoxygenase pathway in ischaemic preconditioning of rat heart
aDepartment of Biochemistry, Faculty of Medicine, University of Tartu, Tartu, Estonia
bDepartment of Medical Physiology, Institute of Medical Biology, University of Tromsø, Tromsø, Norway
* Corresponding author. Tel. (+37-27) 46 52 93; Fax (+37-27) 46 52 90; E-mail: joels@fagmed.uit.no
Objective: Preconditioning with brief intermittent periods of ischaemia is known to provide protection against ischaemic injury. It has been suggested that myocardial ischaemia also activates phospholipase A2, which releases arachidonic acid from phospholipids. In the present study the possible role of phospholipid peroxidation, arachidonic acid and products of the lipoxygenase pathway in cellular mechanisms of ischaemic preconditioning was examined. Methods: Isolated, buffer-perfused rat hearts were freeze-clamped at the end of preconditioning (a cycle of 5 min global ischaemia +5 min reperfusion) and at the end of 30 min global ischaemia and analysed for non-esterified fatty acids and fatty acids in the 2-position of phospholipid. In a separate set of experiments, hearts pretreated with a lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), were subjected to 30 min regional ischaemia and 120 min reperfusion. Infarct size was determined by tetrazolium staining and the ischaemic risk zone with fluorescent particles. Results: Myocardial levels of arachidonic as well as of linoleic and docosahexaenoic acid were significantly elevated by preconditioning. Also, the level of peroxidized polyunsaturated fatty acids (measured as hydroxy conjugated dienes) in myocardial phospholipid was significantly increased: 101.4±16.8 nmol/g versus 51.2±7.3 nmol/g tissue dw in the control group, p<0.05. Pre-treatment of hearts with 5 µM NDGA blocked the infarct limiting effect of preconditioning: infarct size was 37.4±6.4% of risk zone in control, 9.0±0.9% in the preconditioning group and 27.7±3.8% in the preconditioning+NDGA group (p<0.05 vs. IP, n.s. vs. control). Conclusion: Our findings provide evidence for the involvement of phospholipase A2 and lipoxygenase derived lipid second messengers in ischaemic preconditioning of the isolated rat heart.
KEYWORDS Ischemic preconditioning; Arachidonic acid; Phospholipids; Rat heart
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