It is partly responsible for the regulation of potassium, sodium, calcium, and pH. It is the primary site for the kidneys' hormone based regulation of calcium (Ca).
On its apical surface (lumen side), cells of the DCT have a thiazide-sensitive Na-Cl cotransporter and are permeable to Ca, via TRPV5 channel. On the basolateral surface (blood) there is an ATP dependent Na/K antiport pump, a secondary active Na/Ca transporter-- antiport, and an ATP dependent Ca transporter. The basolateral ATP dependent Na/K pump produces the gradient for Na to be absorbed from the apical surface via the Na/Cl synport and for Ca to be reclaimed into the blood by the Na/Ca apical antiport.
It regulates pH by absorbing bicarbonate and secreting protons (H+) into the filtrate, or by absorbing protons and secreting bicarbonate 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. Sodium and chloride (salt) reabsorption is also mediated by a group of kinases called WNK kinases. There are 4 different WNK kinases, WNK1, WNK2, WNK3, and WNK4.
It also participates in calcium regulation by reabsorbing Ca2+ in response to parathyroid hormone
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http://www.answers.com/topic/distal-convoluted-tubule#ixzz1rH7QDbQT
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