What role do kidneys play in acid-base balance?

The kidneys play a crucial role in maintaining acid-base balance by excreting or retaining bicarbonate. Bicarbonate acts as a buffer in the bloodstream, helping to neutralize excess acids and maintain the pH within a narrow range necessary for normal physiological function. When the body is in a state of acidosis (too much acid), the kidneys can retain bicarbonate to counteract this effect, promoting a more alkaline state. Conversely, when the body experiences alkalosis (excess base), the kidneys may excrete more bicarbonate, helping to restore balance.

Though the kidneys also perform filtering operations including the management of hydrogen ions, their primary mechanism for regulating acid-base balance is through the manipulation of bicarbonate levels in response to the body’s needs. This ability to adjust bicarbonate retention or excretion is vital for long-term regulation of acid-base status, complementing the more immediate responses offered by the lungs in controlling carbon dioxide levels. Therefore, the role of excreting or retaining bicarbonate is fundamental in the kidneys' contribution to maintaining the overall acid-base homeostasis within the body.