Fig. 3.

Acute ex vivo effects of P4 and/or 17β-estradiol (E2) on Jo₂ in permeabilized human female myofibers. Rates of Jo₂ (pmol·s⁻¹·mg dry wt⁻¹) and H₂O₂ emission (mE_H2O2) measured in saponin-permeabilized myofibers from lean, healthy women (n = 5) in menstrual cycle follicular phase (days 1–10). Permeabilized fibers were incubated in either DMSO (<1.5%, vehicle), 1.4 nM E2, 60 nM P4, or both (E2 + P4). Substrate conditions were: 25 μM palmitoylcarnitine + 1 mM malate (P-C/M), state 4; P-C/M + 2 mM ADP (+ADP); P-C/M, state 3 + 10 μM cytochrome c (+cyt c); P-C/M, state 3 + 2 mM glutamate (+G); P-C/M, G, state 3 +3 mM succinate (+S). Results are means ± SE (n = 4). *Less than control (DMSO), P < 0.05; **P < 0.01; †less than E2, P < 0.05; ‡less than E2 + P4, P < 0.05.