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This Article Full Text (Publish Ahead of Print[PDF]) All Versions of this Article: 90/6/1532    most recent ajcn.2009.28285v1 Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Mehrotra, R. Articles by Kopple, J. D PubMed PubMed Citation Articles by Mehrotra, R. Articles by Kopple, J. D Agricola Articles by Mehrotra, R. Articles by Kopple, J. D

Effect of high-normal compared with low-normal arterial pH on protein balances in automated peritoneal dialysis patients^1,2,3,4

¹ From the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA (RM, RB, HW, and JDK); the David Geffen School of Medicine at UCLA, Los Angeles, CA (RM and JDK); the Harbor-UCLA Medical Foundation Inc, DaVita Dialysis Unit, Torrance, CA (MA and LT); and the UCLA School of Public Health, Los Angeles, CA (JDK).

² Neither Satellite Health nor DaVita had any role in the study design, or implementation, analysis of results, or interpretation of the data.

³ Supported by NIH grants RR18298 (to RM), DK61389 (to JDK), and M01-RR00425 (to Harbor-UCLA General Clinical Research Center); Satellite Health; and DaVita Inc.

⁴ Address correspondence to R Mehrotra, Division of Nephrology and Hypertension, Los Angeles Biomedical Research Institute, 1124 W Carson Street, Torrance, CA 90502. E-mail: rmehrotra{at}labiomed.org.

ABSTRACT

Background: Although 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.

Objective: We 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.

Design: Eight 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.

Results: The 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.

Conclusion: This 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.

Received for publication June 24, 2009. Accepted for publication September 19, 2009.