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Circulating nitrogen oxide levels. (A) N-nitrosamine (RNNO) and (B) S-nitrosothiol (RSNO) concentrations in blood plasma of Lowlanders and Sherpas at baseline (B) and at early (A1) and late (A2) altitudes are shown. Mean ± SEM (n = 10–12). †P ≤ 0.05 at B vs. A1 within cohort. △P < 0.001 at A1 vs. A2 within cohort.
