QS232. Ischemic Preconditioning Selectively Protects Interfibrillar Mitochondria by Preserving Cytochrome C

Abstract

Purpose: Myocardial mitochondria are grouped into two distinct populations: interfibrillar (IF) and subsarcolemmal (SS) mitochondria. While ischemic preconditioning (IPC) protects overall mitochondrial (mito) function during ischemia-reperfusion (IR), it is unclear whether it has a differential effect on those two mitochondrial populations. The purpose of this study was to elucidate the effects of IPC on IF and SS mitochondria. Method: Isolated rat hearts (n=5/group) were subjected to either a) 40 minutes (min) of equilibration (EQ), 30 min of ischemia (I), and 30 min of reperfusion (RP) (CONTROL) or b) 10 min of EQ, three 5 min episodes of IPC, 30 min I, and 30 min of RP (IPC group). Left ventricular developed pressure (DP) was measured. Mitochondria respiration (state 2, 3, 4, and respiratory control index (state 3/4)) was measured by polarography using glutamate and malate as substrates. Cytochrome c concentration was measured by HPLC. Data is expressed as mean±SEM. Conclusion: Ischemia reperfusion damages IF mitochondria more than SS mitochondria as evidenced by lower cytochrome c levels during reperfusion. IPC protects both IF and SS mitochondria function as evidenced by improved state 3 and RCI. The mechanism of protection of IF mitochondria by IPC may be related to selective preservation of cytochrome c levels during reperfusion.