XFe96 high resolution respiratory assays were utilized on cybrids grown under serum starvation conditions, which promotes OXPHOS. (A) Basal respiration is measured in the presence of non-saturating substrate concentrations (5.6 mM glucose). The addition of oligomycin (inhibits ATP synthesis) reveals ATP production, the uncoupler FCCP (collapses the proton gradient across the mitochondrial inner membrane) reveals the maximum respiration and the spare respiratory capacity, the addition of antimycin A and rotenone (inhibitors of complex III and I) block all mitochondrial function to allow for the determination of non-mitochondrial respiration and proton leak. (B) Averaged traces of ECAR changes in response to oligomycin, FCCP and antimycin A + rotenone. (C) With the exception of spare respiratory capacity, all other features are impaired in J-cybrids. (D) Average ECAR levels changes in response to oligomycin are calculated. (E) OCR and ECAR levels normalized to values measured after antimycin A and rotenone injection were plotted. H-cybrid metabolism at baseline is shifted towards a more aerobic state when compared to J-cybrids, and exhibit a greater dynamic range upon oligomycin treatment. Data is expressed as mean ± stdev, n = 28/29 independent replicates. Student’s t-test *P < 0.05, ** P < 0.01, *** P < 0.001.