Effects of acute metabolic acidosis and alkalosis on leucine metabolism in conscious dogs

To determine the effects of acute metabolic acidosis and alkalosis on leucine metabolism in vivo, mongrel dogs were infused with [1-¹⁴C]leucine for 8 h, along with NaCl, HCl, or NaHCO₃ over the last 4 h. Arterial pH did not change from the basal value during NaCl infusion but decreased (P<.01) and increased (P<.01) during HCl and NaHCO₃ infusions, respectively. Total leucine carbon entry did not change from the basal value during saline infusion but increased (P<.01) with acidosis and decreased (P<.05) with alkalosis. Compared with saline controls, acidosis increased (P<.01) leucine oxidation, whereas alkalosis decreased (P<.01) leucine oxidation. During acidosis, total plasma essential and nonessential amino acid concentrations increased (P<.05), whereas during alkalosis, total plasma essential and nonessential amino acid concentrations decreased (P<.05). These studies suggest that acute alterations in arterial pH may affect the regulation of protein metabolism in vivo and must be considered in the interpretation of results from experiments in which alterations of acid-base homeostasis may have occurred.