Protein levels of mitochondrial respiratory chain complexes (I, II, III, IV, and V) in rapid atrial pacing (RAP) rabbits. A, Western blot results for NDUFB8, SDHB, UQCRC2, MTCO1, and ATP5A protein expression. B, Quantification of NDUFB8, SDHB, UQCRC2, MTCO1, and ATP5A protein levels in the 4 groups. Data are presented as mean ± SD. *P < .05 versus control (CON) group; **P < .01 versus CON group; #P < .05 versus pacing (P7) group; ##P < .01 versus P7 group. NDUEB8 indicates subunit of nicotinamide-adenine dinucleotide dehydrogenase (complex I); SDHB, 30-kDa subunit of succinate dehydrogenase (complex II); UQCRC2, core protein 2 of ubiquinol-cytochrome c reductase complex (complex III); MTCO1, subunit I of cytochrome c oxidase (complex IV); ATP5A, α subunit of F0F1-ATP synthase (complex V); SD, standard deviation.