Effect of diazoxide on flavoprotein oxidation and reactive oxygen species generation during ischemia-reperfusion: a study on Langendorff-perfused rat hearts using optic fibers

1 Institut National de la Santé et de la Recherche Médicale U828; 2 Université Victor Segalen Bordeaux 2; and 3 Centre Hospitalier Universitaire de Bordeaux, Bordeaux, France Submitted 16 November 2007 ; accepted in final form 12 February 2008 This study analyzed the oxidant generation during ischemia-reperfusion protocols of Langendorff-perfused rat hearts, preconditioned with a mitochondrial ATP-sensitive potassium channel (mitoK ATP ) opener (i.e., diazoxide). The autofluorescence of mitochondrial flavoproteins, and that of the total NAD(P)H pool on the one hand and the fluorescence of dyes sensitive to H 2 O 2 or O 2 – [i.e., the dihydrodichlorofluoroscein (H 2 DCF) and dihydroethidine (DHE), respectively] on the other, were noninvasively measured at the surface of the left ventricular wall by means of optic fibers. Isolated perfused rat hearts were subjected to an ischemia-reperfusion protocol. Opening mitoK ATP with diazoxide (100 µM) 1 ) improved the recovery of the rate-pressure product after reperfusion (72 ± 2 vs. 16.8 ± 2.5% of baseline value in control group, P < 0.01), and 2 ) attenuated the oxidant generation during both ischemic (–46 ± 5% H 2 DCF oxidation and –40 ± 3% DHE oxidation vs. control group, P < 0.01) and reperfusion (–26 ± 2% H 2 DCF oxidation and –23 ± 2% DHE oxidation vs. control group, P < 0.01) periods. All of these effects were abolished by coperfusion of 5-hydroxydecanoic acid (500 µM), a mitoK ATP blocker. During the preconditioning phase, diazoxide induced a transient, reversible, and 5-hydroxydecanoic acid-sensitive flavoprotein and H 2 DCF (but not DHE) oxidation. In conclusion, the diazoxide-mediated cardioprotection is supported by a moderate H 2 O 2 production during the preconditioning phase and a strong decrease in oxidant generation during the subsequent ischemic and reperfusion phases. cardioprotection; 5-hydroxydecanoate Address for reprint requests and other correspondence: P. Dos Santos, Inserm U828, Ave. du Haut Lévêque, 33600 Pessac, France (e-mail: pierre.dossantos{at}wanadoo.fr )