White 2018 J Anim Sci
|Differing mitochondrial capacity in two separate skeletal muscles from calm and temperamental Brahman heifers.|
Link: Open Access
Event: J Anim Sci
Muscle mitochondrial capacity has been linked to beef tenderness. Additionally, temperamental cattle often have poorer meat product quality. If mitochondrial capacity in a muscle that is of low commercial value can be used to predict which cattle may have enhanced meat quality, the producer may realize an economic advantage. To test the hypothesis that mitochondrial number and function would be greatest in temperamental animals, and would be higher in the longissimus dorsi (LD) than the trapezius, samples from both muscles were collected from calm (n=6) and temperamental (n=6) 8-mo-old Brahman heifers using a 14-gauge tissue collection needle. Heifer temperament was determined at weaning using pen score and exit velocity. Colorimetric analysis for mitochondrial density (via citrate synthase, CS, activity) and function (via cytochrome c oxidase, COX, activity) was performed on all samples, and mitochondrial capacity was measured utilizing high-resolution respirometry. Data were analyzed using the MIXED procedure of SAS (9.4). Relative to mg tissue (integrative), the LD from temperamental heifers had greater mitochondrial number (CS activity; P<0.0001) and function (COX activity; P=0.002) than the trapezius, while mitochondrial number and function were similar between muscle groups in calm heifers. Mitochondrial density was higher in the LD in temperamental animals compared to calm (P=0.039) but was not different in the trapezius between temperament groups. Integrative maximum electron transport capacity (ECI+II) was also higher in the LD of temperamental compared to calm heifers (P=0.012), but all other integrative capacities were unaffected by temperament and muscle. While also unaffected by temperament, intrinsic (relative to CS activity) mitochondrial state 3 oxidative phosphorylation capacity with complex I substrates (PCI; 6.81 ± 0.48 and 4.31 ± 048 pmol/s*U CS for trapezius and LD, respectively; P=0.002), PCI with complex II substrates (PCI+II; 11.33 ± 0.79 and 6.74 ± 0.79; P=0.0006), electron transport system capacity (ECI+II; 14.06 ± 0.87 and 7.90 ± 0.87; P<0.0001), and ECII (7.88 ± 0.55 and 4.30 ± 0.55, respectively; P=0.0002) were elevated in the trapezius compared to the LD. However, the LD showed a trend for greater fractional control of PCI compared to the trapezius (0.54 ± 0.02 and 0.49 ± 0.01 for LD and trapezius, respectively; P=0.057), indicating greater contribution of CI to energy production in the LD. Temperament was not associated with most measures of mitochondrial function in this study. Future research will delineate if these differences in mitochondria persist throughout the animal’s lifetime, or if they relate to product quality.
Labels: MiParea: Respiration
Organism: Bovines Tissue;cell: Skeletal muscle
Coupling state: OXPHOS Pathway: N HRR: Oxygraph-2k