Omega-3 polyunsaturated fatty acid-enriched diet differentially protects two subpopulations of myocardial mitochondria against Ca2+-induced injury

Omega-3 polyunsaturated fatty acids (PUFA) confer protection against myocardial injury after ischemia-reperfusion. There are two subfractions of mitochondria located in different regions of the cell: subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM). The present study explored possible differences between Ca2+-induced mitochondrial swelling in rat SSM and IFM fractions under control conditions (control group [CG]) and after dietary supplementation with omega-3 PUFA (experimental group [EG]). Changes in mitochondrial matrix volumes were measured using the light-scattering technique. In the CG, the time courses of swelling were comparable in both mitochondrial fractions, with no difference in Ca2+-induced swelling between the two mitochondrial fractions. In the SSM fraction, no difference in the time course of swelling in Ca2+-free solution between CG and EG was detected. In the EG, both SSM and IFM fractions demonstrated a decreased sensitivity to Ca2+; IFM fractions, however, exhibited significantly less pronounced swelling following Ca2+ addition. The authors conclude that IFM and SSM fractions do not differ in their sensitivity to Ca2+-induced swelling. While dietary omega-3 PUFA protected both mitochondrial fractions against Ca(2+-)evoked swelling, the protective effect appeared to be more pronounced for the IFM fraction than for the SSM fraction.