Distal convoluted tubule

Distal convoluted tubule
Kidney nephron.png
Kidney nephron ("1st proximal convoluted tubule", "2nd distal convoluted tubule")
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Section of cortex of human kidney.
Latin tubulus contortus distalis
Gray's subject #253 1223
Precursor Metanephric blastema
MeSH Distal+Kidney+Tubule

The distal convoluted tubule (DCT) is a portion of kidney nephron between the loop of Henle and the collecting duct system.

Contents

Physiology

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.

  • 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. [1] PTH effect is mediated through phosphorylation of regulatory proteins and enhancing the synthesis of all transporters within the distal convoluted tubule.

Clinical significance

Thiazide diuretics inhibit Na+/Cl- reabsorption from the DCT by blocking the thiazide-sensitive Na-Cl cotransporter.

By inhibiting the cotransporter, 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 that are shorter than those of the proximal convoluted tubule (PCT). The lumen appears larger in DCT than the PCT lumen because the PCT has a brush border (microvilli). DCT can be recognized by its numerous mitochondria, basal infoldings and lateral membrane interdigitations with neighboring cells.

The point where DCT contacts afferent arteriole of renal corpuscle is called macula densa. It has tightly packed columnar cells which display reversed polarity and may monitor the osmolarity of blood.

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

Characteristic PCT DCT
Apical brush border Usually present Not present
Eosinophilicity More Less
Cytoplasm More Less
Readily discernible nuclei Less likely More likely

Additional images

References

  1. ^ MedEd at Loyola mech/cases/case24/kidney.htm

External links


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Look at other dictionaries:

  • distal convoluted tubule — n the convoluted portion of the nephron lying between the loop of Henle and the nonsecretory part of the nephron and concerned esp. with the concentration of urine called also convoluted tubule, distal tubule * * * tubulus contortus distalis …   Medical dictionary

  • distal convoluted tubule — noun : the convoluted portion of the vertebrate nephron that lies between the loop of Henle and the collecting tubule in intimate association with the afferent vessel, that resembles the proximal convoluted tubule in structure though lacking the… …   Useful english dictionary

  • distal convoluted tubule — noun Date: circa 1901 the convoluted portion of the vertebrate nephron that lies between the loop of Henle and the nonsecretory part of the nephron and that is concerned especially with the concentration of urine …   New Collegiate Dictionary

  • convoluted tubule — n 1) PROXIMAL CONVOLUTED TUBULE 2) DISTAL CONVOLUTED TUBULE * * * a channel that follows a tortuous course; see tubulus contortus distalis, tubulus contortus proximalis, and tubuli seminiferi contorti …   Medical dictionary

  • convoluted tubule — noun Date: 1923 all or part of the coiled sections of a nephron: a. proximal convoluted tubule b. distal convoluted tubule …   New Collegiate Dictionary

  • convoluted tubule — noun 1. : proximal convoluted tubule 2. : distal convoluted tubule * * * n. Anat. a portion of the nephron in the kidney that functions in concentrating urine and in maintaining salt, water, and sugar balance. [1945 50] …   Useful english dictionary

  • proximal convoluted tubule — noun : the convoluted portion of the vertebrate nephron that lies between the Malpighian corpuscle and the loop of Heule, is made up of a single layer of cuboidal cells with striated borders, and is believed to be concerned especially with the… …   Useful english dictionary

  • Tubule — A small tube. * * * A small tube. SYN: tubulus [TA]. [L. tubulus, dim. of tubus, tube] Albarran y Dominguez tubules SYN: Albarran glands, under gland. connecting t. a narrow arching t. of the kidney joining the distal convoluted t. and the… …   Medical dictionary

  • Connecting tubule — Scheme of renal tubule and its vascular supply. Latin tubulus renalis arcuatus Gray s …   Wikipedia

  • renal tubule — n the part of a nephron that leads away from a glomerulus, that is made up of a proximal convoluted tubule, loop of Henle, and distal convoluted tubule, and that empties into a collecting tubule * * * the fine tubular part of a nephron, through… …   Medical dictionary

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