Network distribution of mitochondria and lipid droplets in human muscle Wbres

Abstract The objective of the present study was to develop a combination of Xuorescent stains that would allow visualisation of the network of mitochondria and lipid droplets (intramyocellular lipids or IMCL) in human skeletal muscle Wbres by means of conventional and confo-cal microscopy. Muscle biopsies were taken from the vas-tus lateralis of three lean, healthy and physically active male subjects. Frozen muscle sections were stained for mitochondria using antibodies against three mitochondrial proteins; porin, cytochrome c oxidase (COX) and NADH-ubiquinol oxidoreductase and neutral lipids were stained with oil red O. Anti-COX staining produced images with the strongest Xuorescence signal and the highest resolution of the mitochondrial network and this stain was success-fully combined with the antibody against type I Wbre myo-sin. A highly organised matrix arrangement of mitochondria within the sarcomeres (in pairs at the I-band) was observed in the oxidative type I Wbres. The density of mitochondria was the highest in the subsarcolemmal region. Anti-COX staining was combined with oil red O demonstrating that in type I Wbres lipid droplets are mainly located in the space between the mitochondria