 The kidneys play a crucial role in maintaining proper acid-base balance by secreting either acid or base into the urine through specialized cells called intercalated cells. These cells express the sodium-dependent chloride by carbonatex changer AE4, which is responsible for detecting changes in acidity levels and adjusting accordingly. When AE4 is absent, mice experience severe disruptions in their ability to sense and respond to changes in acid-base balance. This leads to a failure to properly regulate metabolic alkalosis and acidosis, resulting in serious health complications. This article was authored by H. Bittstam, M. Koch, L. Eckerman, and others.