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. 2021 Jun 28;12:689684. doi: 10.3389/fphys.2021.689684

FIGURE 5.

FIGURE 5

Mitochondrial efficiency of ATP production and O2 affinity in juvenile snapping turtles from normoxic (21% O2; N21) and hypoxic (10% O2; H10) incubations. (A) P:O ratio. Oxygen concentration as a function of time is shown for normoxic (n = 5) and hypoxic (n = 5) developmental groups. Solid lines correspond to the line of best-fit. The inset graph shows the mean P:O values (±SEM). (B) The respiratory-control ratio (RCR) and (C) OXPHOS coupling efficiency ratio were calculated for normoxic (n = 5–8) and hypoxic (n = 5–8) developmental groups. Both ratios were measured in the presence of complex-I subtrastes. (D) Mitochondrial oxygen affinity. Respiration rate (VO2) as a function of oxygen concentration is shown, with individual curves plotted for normoxic (n = 5) and hypoxic (n = 5) incubation. The inset graph shows the mean P50 values ± SEM. Calculations for all variables are given in Section “Materials and Methods.” Statistical significance was assessed with individual generalized linear models, followed by Sidak post hoc tests, to assess the effect of developmental O2 (N21 vs. H10). Values were considered significant when P ≤ 0.05, which are denoted by asterisks (*).