Distal convoluted tubule

Source: Wikipedia, the free encyclopedia.
Distal convoluted tubule
Kidney nephron ("1st proximal convoluted tubule", "2nd distal convoluted tubule")
Section of cortex of human kidney.
Details
PrecursorMetanephrogenic blastema
Identifiers
Latintubulus contortus distalis
FMA17721
Anatomical terminology

The distal convoluted tubule (DCT) is a portion of

collecting tubule
.

Physiology

It is partly responsible for the regulation of potassium, sodium, calcium, and pH.

On its

basolateral surface (peritubular capillary side) there is an ATP-dependent Na/K antiporter 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
, and for Ca to be reclaimed into the blood by the Na/Ca basolateral antiporter.

  • 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.[1] 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-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 that are shorter than those of the

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

proximal convoluted tubule
:

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

Additional images

  • 1 Glomerulus, 2 proximal tubule, 3 distal tubule
    1
    proximal tubule
    , 3 distal tubule
  • Transverse section of pyramidal substance of kidney of pig, the bloodvessels of which are injected.
    Transverse section of pyramidal substance of kidney of pig, the bloodvessels of which are injected.
  • Renal corpuscle
    Renal corpuscle
  • Diagram outlining movement of ions in nephron.
    Diagram outlining movement of ions in nephron.

See also

List of distinct cell types in the adult human body

References

External links