The effect of oral protein loading on renal acidification in patients with heart failure

BACKGROUND The purpose of this study was to explore the renal acid-base response to acute protein load in patients with heart failure (HF). It was prompted by the fact that there are no data available regarding the role of renal tubules in maintaining acid-base balance following protein loading in HF patients. METHODS AND RESULTS Nine male patients with HF and 12 healthy subjects (controls) were enrolled in this study. In the HF patients, average blood pH was 7.42 (0.03), average pCO2 was 36.6 mmHg (6.3) and average bicarbonate was 24.2 mmol/L (4.3). The acid-base status of patients was unaffected by meat ingestion. The values at peak glomerular filtration rate (GFR) did not differ significantly from baseline levels. An oral protein load did not influence the urinary pH, titratable acidity (TA) and ammonium excretion in the patients with HF, contrary to the findings in the controls. On the other hand, ammonium excretion in patients with HF reduced significantly compared with values from controls at baseline and following oral protein loading. Filtered and reabsorbed bicarbonate increased significantly in HF patients following meat ingestion, whereas there was no change in absolute and fractional bicarbonate excretion and fractional bicarbonate reabsorbed. CONCLUSIONS This study demonstrated that in patients with HF, bicarbonate reabsorption increases following an oral protein load without a significant enhancement in bicarbonate excretion. The difference can be explained by the presence of respiratory alkalosis leading to bicarbonate conservation.