Effect of high-normal compared with low-normal arterial pH on protein balances in automated peritoneal dialysis patients

Abstract

BackgroundAlthough the protein catabolic effects of metabolic acidosis are well established, it is unclear whether the entire reference range of arterial pH (7.37–7.44) is equivalent for protein balance. ObjectiveWe undertook this study to test the hypothesis that in patients undergoing automated peritoneal dialysis, an arterial pH of 7.43–7.45, as compared with a pH of 7.36–7.38, is associated with more-positive nitrogen balances. DesignEight stable subjects (5 men) aged 43.1 ± 15.3 y completed a randomized, crossover nitrogen balance study for ≥42 d. Arterial pH was varied by changing the daily doses of sodium citrate/citric acid and ammonium chloride. ResultsThe subjects attained mean (±SD) arterial pH values of 7.37 ± 0.01 and 7.44 ± 0.02 during the low-normal and high-normal pH phases, respectively. The higher arterial pH was associated with higher net nitrogen balances (3.22 ± 1.37 compared with 2.29 ± 2.18 g/d; P = 0.06), lower serum urea nitrogen (54.1 ± 13.7 compared with 64.4 ± 20.2 mg/dL; P = 0.01), higher fasting leucine flux (P = 0.02), and increased fasting total-body protein synthesis (P = 0.01) and degradation (P = 0.02). In 7 of 8 study subjects, nitrogen balances were more positive at the higher arterial pH (P = 0.004). There were no significant changes in anthropometric measurements, other biochemical measurements, and the mRNA content of selected proteins in skeletal muscle. ConclusionThis study suggests that in most stable automated peritoneal dialysis patients, a mean arterial pH of 7.44, as compared with 7.37, is associated with more-positive nitrogen balances. This trial was registered at clinical trials.gov as NCT00586131.