The distal convoluted tubule (DCT) is a portion of kidney nephron between the loop of Henle and the collecting duct system. It is partly responsible for the regulation of potassium, sodium, calcium, and pH.

Physiology

The DCT regulates pH by absorbing bicarbonate and secreting protons (H⁺) into the filtrate. Sodium and potassium levels are controlled by secreting K⁺ and absorbing Na⁺.

Sodium absorption by the distal tubule is mediated by the hormone aldosterone. Aldosterone increases sodium reabsorption.

The DCT also participates in calcium regulation by absorbing Ca²⁺ in response to parathyroid hormone.

Thiazide diuretics inhibit Na⁺/Cl^- reabsorption from the DCT.

Histology

Histologically, cells of the DCT can be differentiated from cells of the proximal convoluted tubule since: -

• DCT cells do not have an apical brush border
• DCT cells are less eosinophilic than proximal cells
• DCT cells have less cytoplasm
• DCT cells are more likely to have visible nuclei

External links

• Kidney function - Loyola University (http://www.meddean.luc.edu/lumen/meded/mech/cases/case24/kidney.htm)
• Calcium regulation - Cornell University (http://web.vet.cornell.edu/public/popmed/clinpath/CPmodules/chem/capmg.htm)