Role of K(ir)5.1 (Kcnj16) Channels in Regulating Renal Ammonia Metabolism during Metabolic Acidosis in Dahl Salt-Sensitive Rats.

Maintaining acid-base homeostasis is critical for normal physiological function. The kidneys are essential for regulating acid-base homeostasis through maintaining systemic bicarbonate concentration. Chronic metabolic acidosis is an independent risk factor for chronic kidney diseases. Renal inwardly rectifying potassium channel K(ir)5.1 plays an essential role in maintaining resting membrane potential. Patients with loss-of-function mutations in the KCNJ16 gene, which encodes K(ir)5.1, may have tubulopathy with hypokalemia, salt wasting, and hearing loss. Importantly, these mutations also disrupt acid-base balance, particularly causing metabolic acidosis. This study aimed to use Dahl salt-sensitive rats with a knockout of the Kcnj16 gene (SS(Kcnj16-/-)) to investigate how the deletion of K(ir)5.1 affects the regulation of acid-base balance in salt-sensitive hypertension. SS(Kcnj16-/-) rats displayed metabolic acidosis under a normal salt diet. Further analysis using RNA sequencing and Western blot analyses showed unchanged expression of proteins responsible for ammonia metabolism in the kidney of SS(Kcnj16-/-) rats despite observed acidosis. However, there was a significant increase in the expression of bicarbonate transporter NBCe1, where there was a significant decrease in pendrin. In conclusion, the current study demonstrated that the loss of K(ir)5.1 impairs the sensitivity of ammonia metabolism in the kidney in response to metabolic acidosis, which provides mechanistic insights into developing potential therapeutics for conditions involving hypokalemia and acid-base abnormalities.