The distal convoluted tubule (DCT) is a portion of

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

nephron The nephron is the minute or microscopic structural and functional unit of the kidney. It is composed of a renal corpuscle and a renal tubule. The renal corpuscle consists of a tuft of capillaries called a glomerulus and a cup-shaped structu ...

between the

loop of Henle In the kidney, the loop of Henle () (or Henle's loop, Henle loop, nephron loop or its Latin counterpart ''ansa nephroni'') is the portion of a nephron that leads from the proximal convoluted tubule to the distal convoluted tubule. Named after it ...

and the collecting tubule.

Physiology

It is partly responsible for the regulation of

potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

, and pH. On its apical surface (lumen side), cells of the DCT have a thiazide-sensitive Na-Cl cotransporter and are permeable to Ca, via the

TRPV5 Transient receptor potential cation channel subfamily V member 5 is a calcium channel protein that in humans is encoded by the ''TRPV5'' gene. Function The ''TRPV5'' gene is a member of the transient receptor family and the TRPV subfamily. Th ...

channel. On the basolateral surface (peritubular capillary side) there is an ATP-dependent Na/K

antiporter An antiporter (also called exchanger or counter-transporter) is an integral membrane protein that uses secondary active transport to move two or more molecules in opposite directions across a phospholipid membrane. It is a type of cotransporte ...

pump, a secondary active Na/Ca transporter, 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

symporter A symporter is an integral membrane protein that is involved in the transport of two (or more) different molecules across the cell membrane in the same direction. The symporter works in the plasma membrane and molecules are transported across th ...

, and for Ca to be reclaimed into the blood by the Na/Ca basolateral antiporter. * It regulates pH by absorbing

bicarbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial bioche ...

and secreting

proton A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...

s (H⁺) into the filtrate, or by absorbing

s and secreting

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 A hormone (from the Ancient Greek, Greek participle , "setting in motion") is a class of cell signaling, signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physio ...

aldosterone Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays ...

. 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, , , , and . * It also participates in

regulation by reabsorbing Ca²⁺ in response to parathyroid hormone. PTH effect is mediated through phosphorylation of regulatory proteins and enhancing the synthesis of all transporters within the distal convoluted tubule. * Arginine vasopressin receptor 2 is also expressed in the DCT.

Clinical significance

Thiazide Thiazide () refers to both a class of sulfur-containing organic molecules and a class of diuretics based on the chemical structure of benzothiadiazine. The thiazide drug class was discovered and developed at Merck and Co. in the 1950s. The firs ...

diuretic A diuretic () is any substance that promotes diuresis, the increased production of urine. This includes forced diuresis. A diuretic tablet is sometimes colloquially called a water tablet. There are several categories of diuretics. All diuretics ...

s inhibit Na⁺/Cl⁻ reabsorption from the DCT by blocking the thiazide-sensitive Na-Cl cotransporter. By inhibiting the transporter, thiazide diuretics increase the gradient potential for Na. This increases the activity of the basolateral Na/Ca antiport and causes the increase in calcium reclamation associated with thiazide diuretics.

Histology

The DCT is lined with simple cuboidal cells, the distal convoluted tubule cells, that are shorter than those of the proximal convoluted tubule (PCT). The lumen appears larger in the PCT than the DCT lumen because the PCT has a brush border (microvilli). DCT can be recognized by its numerous

mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

(even though it is not as much as PCT), basal enfoldings and lateral membrane interdigitations with neighboring cells. The point where DCT contacts the cortical thick ascending limb of the

is called macula densa. It has tightly packed columnar cells which display reversed polarity and may monitor the osmolarity of blood.

Histologically Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...

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

Additional images

Image:Histology-kidney.jpg , 1 Glomerulus, 2

proximal tubule The proximal tubule is the segment of the nephron in kidneys which begins from the renal (tubular) pole of the Bowman's capsule to the beginning of loop of Henle. At this location, the glomerular parietal epithelial cells (PECs) lining bowman’s ...

, 3 distal tubule Image:Gray1133.png, Transverse section of pyramidal substance of kidney of pig, the bloodvessels of which are injected. Image:Renal corpuscle-en.svg, Renal corpuscle Image:Kidney nephron molar transport diagram.svg, Diagram outlining movement of ions in nephron.

References

External links