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
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 and secreting
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 ...
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
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 ...
regulation by reabsorbing Ca
2+ 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
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 ...
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.
See also
List of distinct cell types in the adult human body
The list of human cell types provides an enumeration and description of the various specialized cells found within the human body, highlighting their distinct functions, characteristics, and contributions to overall physiological processes. Cell ...
References
External links
*
*
{{Urinary system anatomy
Kidney anatomy
fr:Néphron#Tubule contourné distal