Application of 2H2O to quantify red blood cell protein synthesis rates in young trained and untrained males and females

AimCompare the fractional synthetic rate (FSR) of hemoglobin in trained and untrained humans (Hb FSR). MethodsWe employed deuterated water (2H2O) to measure Hb FSR in young males (n=10) and females (n=10) who were aerobically trained (n=5 per sex) and untrained (n=5 per sex). Overall, participants had a mean [Formula] of 49.8 [SD: 10.9] mL/kg/min, hemoglobin mass of 775 [180] g, and red blood cell volume of 2370 [550] mL. After an initial loading dose, participants ingested 2H2O daily for 28 days to maintain a stable 2H body water enrichment ([~]0.9 atom percent deuterium (APD)), as measured in saliva samples collected every 2-3 days. 2H-enriched alanine was measured in RBC protein using gas chromatography combustion isotope ratio mass spectrometry. ResultsThe increase in APD for Hb protein was nonlinear for the first two weeks, but stabilized from day 14 to day 28, with mean APD reaching 0.033 [0.005] % on day 28. Hb FSR calculated over this 2-week period was 0.84 [0.15] %/day, which equated to an Hb absolute synthetic rate of 6.5 [2.2] g/day and a lifespan of 126 [30] days. Hb FSR was not different trained (0.83 [0.19] %/day) and untrained (0.86 [0.24] %/day, P=0.81) individuals or between males (0.80 [0.25] %/day) and females (0.88 [0.17] %/day), P=0.24). ConclusionHabitual endurance training does not appear to affect Hb FSR, but the use of 2H2O to measure Hb FSR in humans has potential applications to many experimental and clinical scenarios.