Reabsorptie en secretie in de DCT en verzamelbuis

The early part of the distal convoluted tube, or DCT, reabsorbs around 10 to 15% of the filtered water and 5% of the filtered sodium and chloride ions.

Sodium and chloride are reabsorbed via Na⁺– Cl⁻ symporters in the apical membranes. These ions then move into the peritubular capillaries through sodium-potassium pumps and Cl⁻ leakage channels.

The early DCT is also responsible for reabsorbing the majority of calcium ions in response to parathyroid hormone.

Two types of cells — principal and intercalated cells — are present in the distal part of the DCT and throughout the collecting ducts.

The principal cells reabsorb sodium ions via sodium leakage channels and secrete potassium ions.

The intercalated cells reabsorb bicarbonate ions and secrete hydrogen ions, thereby regulating blood pH.

Under circumstances like dehydration or low blood volume, the hormone ADH makes the cells in the distal part of the DCT and the collecting ducts permeable to water.

The adrenal cortex releases aldosterone to upregulate sodium reabsorption. As a result, water follows sodium along the osmotic gradients.