Diazoxide prevents mitochondrial swelling and Ca2+ accumulation in CA1 pyramidal cells after cerebral ischemia in newborn pigs.
Diazoxide (DIAZ), an opener of mitochondrial ATP-sensitive K(+) channels (mK(ATP)), protects neurons against hypoxic/ischemic stress in vivo, however, direct evidence showing mitochondrial effects of DIAZ in postischemic neurons is lacking. We investigated if DIAZ affects mitochondrial alterations after global ischemia/reperfusion (I/R) in CA1 pyramidal neurons by using oxalate-pyroantimonate electron cytochemistry. Anesthetized piglets were either non-treated, or treated with DIAZ (3 mg/kg, iv), I/R, DIAZ+I/R, or 5-hydroxy-decanoate (5HD)+DIAZ+I/R (n=6, 6, 11, 5, 7, respectively). Ischemia (10 min) was induced by intracranial pressure (ICP) elevation. After 5-30 min of reperfusion, the brains were fixed for ultrastructural studies. Relative volumes of Ca(2+)-containing deposits and mitochondria in CA1 pyramidal cells were determined by point counting on electron micrographs. I/R resulted in maximal increases in mitochondrial volume (from 7.14+/-0.63% to 9.74+/-0.57%*), and Ca(2+) levels (from 5.86+/-1.11% to 11.39+/-1.35%*; mean+/-S.E.M., *p<0.05) at 10-15-min reperfusion time. In this interval, pretreatment with DIAZ virtually abolished mitochondrial swelling (6.88+/-0.49%) and Ca(2+) accumulation (5.15+/-0.82%) evoked by I/R. The protective effect of DIAZ was reduced by 5HD, an inhibitor of mK(ATP), resulting in a calcium accumulation similar to that after IR (10.44+/-1.98%). Thus, DIAZ might preserve mitochondrial integrity in CA1 pyramidal cells after I/R, at least in part mediated by mK(ATP).
Domoki
Ferenc
F
Department of Physiology, Faculty of Medicine, University of Szeged, Szeged, Dóm tér 10. H-6720, Hungary. dooki@phys.szote.u-szeged.hu
Bari
Ferenc
F
Nagy
Krisztina
K
Busija
David W
DW
Siklós
László
L
D000818:Animals; D000831:Animals, Newborn; D002545:Brain Ischemia / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D002118:Calcium / Q000378:metabolism*; D003981:Diazoxide / Q000494:pharmacology* / Q000627:therapeutic use; D005260:Female; D008297:Male; D008933:Mitochondrial Swelling / Q000187:drug effects* / Q000502:physiology; D017966:Pyramidal Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D013552:Swine
D003981:Diazoxide; D002118:Calcium