title: Dual effects of dichloroacetate on cardiac ischaemic preconditioning in the rat isolated perfused heart.
abstract: 1. Ischaemic cardiac preconditioning represents an important cardioprotective mechanism which limits myocardial ischaemic damage. The aim of this investigation was to assess the impact of dichloroacetate (DCA), a pyruvate dehydrogenase complex activator, on preconditioning. 2. Rat isolated hearts were perfused by use of the Langendorff technique, and were subjected to either preconditioning (3 x 4 or 3 x 6 min ischaemia) or continuous perfusion, followed by 30 min global ischaemia and 60 min reperfusion. DCA (3 mM) was either given throughout the protocol (pretreatment), during reperfusion only (post-treatment), or not at all. Throughout reperfusion mechanical performance was assessed as the rate-pressure product (RPP: left ventricular developed pressure x heart rate). 3. In non-preconditioned control hearts, mechanical performance was substantially (P < 0.001) depressed on reperfusion (the RPP after 60 min of reperfusion (RPP(t=60)) was 4,246+/-974 mmHg beats min(-1) compared to baseline value of 21,297+/-1,728 mmHg beats min(-1)). Preconditioning with either 3 x 4 min or 3 x 6 min cycles caused significant protection, as shown by enhanced recovery (RPP(t=60) = 7,818+/-1,138, P < 0.05, and 11,123+/-587 mmHg beats min(-1), P < 0.001, respectively). 4. Addition of DCA (3 mM) to hearts under baseline conditions significantly (P < 0.001) enhanced systolic function with an increased left ventricular developed pressure of 108+/-5 mmHg compared to 88.3+/-3.0 mmHg in the controls. 5. Pretreatment with 3 mM DCA had no effect on recovery of mechanical performance in the non-preconditioned hearts (RPP(t=60) = 3,640+/-1,235 mmHg beats min(-1)) while the beneficial effects of preconditioning were reduced in the preconditioned hearts (3 x 4 min: RPP(t=60) = 2,919+/-1,060 mmHg beats min(-1); 3 x 6 min: RPP(t=60) = 8,032+/-1,367 mmHg beats min(-1)). Therefore, DCA had increased the threshold for preconditioning. 6. By contrast, post-treatment of hearts with 3 mM DCA substantially improved recovery on reperfusion in all groups (RPP(t=60) = 5,827+/-1,328 (non-preconditioned), 14,022+/-3,743 (3 x 4 min; P < 0.01) and 23,219+/-1,374 (3 x 6 min; P < 0.001) mmHg beats min(-1)). 7. The results of the present investigation clearly show that pretreatment with DCA enhances baseline cardiac mechanical performance but increases the threshold for cardiac preconditioning. However, post-treatment with DCA substantially augments the beneficial effects of preconditioning.
authors.affiliation: School of Biomedical Sciences, University of Nottingham Medical School.
authors.forename: M D
authors.initials: MD
authors.lastname: Randall
authors.forename: C A
authors.initials: CA
authors.lastname: Keon
authors.forename: P L
authors.initials: PL
authors.lastname: Greenhaff
authors.forename: D
authors.initials: D
authors.lastname: Constantin-Teodosiu
mesh_terms: D000818:Animals; D003999:Dichloroacetic Acid / Q000494:pharmacology*; D004734:Energy Metabolism; D004789:Enzyme Activation; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D017202:Myocardial Ischemia / Q000201:enzymology; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D011768:Pyruvate Dehydrogenase Complex; D003999:Dichloroacetic Acid