What is the most potent stimulus for H+ secretion in the kidney?

The most potent stimulus for H+ secretion in the kidney is a decrease in potassium levels. When there are lower levels of potassium (hypokalemia), the body reacts by increasing hydrogen ion (H+) secretion in the renal tubules, specifically in the proximal tubule and the collecting duct. This occurs because of the need to maintain electroneutrality within the renal tubules; when potassium is low, secreting H+ ions helps balance the charge. This is critical for maintaining acid-base homeostasis in the body, as the kidneys play a key role in regulating pH by adjusting H+ and bicarbonate levels.

In addition, a decrease in plasma potassium can stimulate the secretion of aldosterone, which promotes H+ secretion as well, further enhancing the kidney's ability to excrete acid. The dynamic response of the kidneys reflects the interaction between electrolyte levels and acid-base regulation, showing how closely linked these systems are in maintaining physiological balance.