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Renal Tubules Transport Mechanisms Flashcards

1
Q

What are the three methods of passive transport that occurs in the kidneys?

A

Diffusion
Osmosis
Electrochemical gradients

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2
Q

What are the two types of active transport which occurs in the Kidneys?

A

Primary Active Transport and Secondary Active Transport

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3
Q

How is endocytosis used in the renal tubules?

A

Small proteins are reabsorbed in the proximal convoluted tubules

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4
Q

What is an example of a symporter?

A

The Na+ / Glucose Symporter

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5
Q

How do symporters and antiporters provide methods of secondary active transport?

A

Involves the coupled transport of two or more ions, one moves down electrochemical gradient which provides energy for the movement of another up the electrochemical gradient

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6
Q

Describe how Na+ / K+ ATPase Pumps work?

A

one molecule of ATP is used to Pump 3 x Na+ out the cell, into the blood and 2 x K into the cell from the blood

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7
Q

How does the presence of Na + / K+ ATPase Pumps on the basolateral membrane help the transportation of other substances?

A

The movement of 3 x Na+ out the cell into the blood creates a low concentration of Na+ within the cell

Therefore, on the apical side, Na+ moves into the Cell, down the electrochemical gradient through a syn/antiporter which therefore transports another molecule up their concentration gradient

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8
Q

Describe the reabsorption of sodium in the Early Proximal Convoluted Tubule?

A
  1. Na+ / K+ ATPase Pump creates low Na+ inside cell
  2. Na+ moves through Na+ / H+ Anti Porter on Apical Side, as H+ moves into tubular fluid - this H+ is generated through the breakdown of Water and carbon Dioxide by carbonic Anhydrase
  3. Then Na+ moves through Na+ / HCO3- Symporter on Basolateral side into blood
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9
Q

Describe the reabsoprtion of HCO3- in the early proximal convoluted tubule

A
  1. Na+ / K+ ATPase Pump creates low Na+ inside cell
  2. Carbonic Anhydrase converts water and co2 into H+ and HCO3-
  3. Na+ moves through Na+ / H+ Anti Porter on Apical Side into the cell, as H+ moves into tubular fluid
  4. Then Na+ and HCO3- move through Na+ / HCO3- Symporter on Basolateral side into blood
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10
Q

How does Angiotensin II regulate Na+ reabsorption in the Early Proximal Convoluted tubule?

A

By Increasing the number of Na+ / H+ Antiporters

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11
Q

What happens to sodium, bicarbonate and glucose in the Early Proximal CT?

A

Sodium - Reabsorbed
Bicarbonate - Reabsorbed
Glucose - Reabsorbed

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12
Q

Describe the reabsorption of glucose into the Blood in the Early Proximal Convoluted Tubule?

A
    1. Na+ / K+ ATPase Pump creates low Na+ inside cell
  2. Na+ and glucose from tubular fluid moves through Na+ / Glucose Symporter on Apical Side
  3. Then glucose moves through GLUT2 transporter on the basolateral side into the blood
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13
Q

What is the name of the Na+ / H+ Antiporter found on the apical side of the Early Proximal Convoluted Tubule?

A

NHE3

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14
Q

What is the name of the Na+ / Glucose Symporter found on the apical side of the Early Proximal Convoluted Tubule?

A

SGLT2

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15
Q

What percentage of glucose is reabsorbed in the Early Proximal Convoluted tubule

A

100%

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16
Q

What percentage of Water, Na+ and Cl- are reabsorbed in the Early Proximal Convoluted Tubule?

A

67% Water
67% Na+
67% Cl-

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17
Q

What percentage of amino acids are reabsorbed in the early Proximal Convoluted tubule?

A

100%

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18
Q

What percentage of bicarbonate is reabsorbed in the Early Proximal Convoluted Tubule?

A

80%

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19
Q

What substances are secreted in the Early Proximal Convoluted Tubule?

A

Drugs, Ammonia, Bile Salts, Prostaglandins, Vitamins

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20
Q

What is the osmolarity of the fluid entering the LOH?

A

Isosmotic

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21
Q

Is Na+ Cl+ reabsorbed in the descending LOH?

A

No

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22
Q

What is passively reabsorbed in the descending LOH?

23
Q

Where is Na+ and Cl- passively reabsorbed?

A

Thin ascending LOH

24
Q

Where is Na+ Cl- actively reabsorbed?

A

Thick ascending LOH

25
Is Water reabsorbed in the ascending LOH?
No
26
Why does water get passively reabsorbed in the descending LOH?
In the Ascending LOH, alot of Na + and Cl - is being reabsorbed into medullary interstitium, creating low H20 in interstitium. Therefore, by simple osmosis which is passive transport H2O can move from Descending LOH into the hyperosmotic medullary interstitium
27
What is the osmolarity of the medullary interstitium?
Hyperosmotic
28
What is the osmolarity of the tubular fluid after passing down the descending limb?
Hyperosmotic (Little water)
29
What is the osmolarity of the tubular fluid after passing up the ascending limb of the LOH?
Hypoosmotic (Alot of water)
30
What substances are reabsorbed in the LOH?
25% Na+, 25% Cl- and 15% H2O
31
What is the symporter found on the apical side of the LOH?
Na+ - K+ - 2Cl- Symporter - Moves all these ions into the cell
32
What is the symporter found in the basolateral side of the LOH?
K+ Cl- Symporter
33
Which cations are reabsorbed paracellularly in the LOH?
Na+, Ca2+, K+ and Mg2+
34
Describe how Na+ and Cl- is actively reabsorbed in the Thick Ascending limb of the LOH?
1. Na+ / K+ ATPase Pumps Na+ out and K+ in 2. Creates Gradient for the Na+ K+ 2Cl- Symporter to pump these ions into the cell on the apical side 3. Then, K+ Cl- Symporter on Basolateral side transports both ions into the Blood - K+ moving down conc gradient, Cl- moving against
35
What three substances are reabsorbed in the early DISTAL convoluted tubule?
Na+ Cl- and Active Ca2+ reabsorption
36
Are aquaporin molecules found in the early distal CT?
No - they are absent
37
What is a key ion that is absorbed in the Early Distal CT?
Ca2+
38
By what two transporters is Ca2+ reabsorbed in the Early Distal CT?
Na+ Ca2+ Antiporter | Ca2+ ATPase Pump
39
How does Ca2+ enter into the cell from the tubular fluid?
Via Ca2+ channels
40
How is Na+ and Cl- reabsorbed in the Early Distal Convoluted Tubule?
Na+ K+ ATPase Pump brings Na+ out cell, creating low conc within and K+ into cell, creating high conc within Na+ Cl- Symporter brings Na+ and Cl- into the cell K+ Cl- Symporter brings both into the blood
41
What are the two cell types are found in the late distal CT and Collecting Duct?
Principal Cells and Intercalated Cells
42
What is the primary role of the principal cells?
Na+ reabsorption and K+ Secretion
43
In what situation does the role of the principal cells become very important?
In Hyperkalaemia - where there is too much K+ in the body, so it is secreted out the blood into the tubule and out the body as urine
44
In the Late Distal CT and CD, where are aquaporin molecules always found?
Basolateral side
45
How does Aldosterone regulate Na+ reabsorption in the LDCT and CD?
1. Increases Apical Na+ channels | 2. Increases basolateral Na+ K+ ATPase pumps
46
How does ADH regulate water reabsoprtion in the LDCT and CD?
Increases apical Aquaporin molecules
47
What is the role of the intercalated cell?
Maintaining acid-base balance
48
What happens in the alpha Intercalated cells?
HCO3- Reabsorption into blood | H+ Secretion into fluid
49
What happens in the beta intercalated cells?
HCO3- secretion into fluid | H+ reabsorption into blood
50
Which intercalated cells are active during alkalosis and why?
Alkalosis = blood is too alkaline, therefore beta intercalated cells are used as H+ into blood reabsorption occurs there
51
Where is the H+ ATPase pump located in the alpha Intercalated cells in the LDCT and CD?
Apical Side
52
Where is the H+ ATPase pump located in the beta Intercalated cells in the LDCT and CD?
Basolateral side
53
Where is the Cl- HCO3- Anti-porter located in alpha and beta intercalated cells?
``` Alpha = basolateral side Beta = Apical Side ```
54
Describe how principal cells facilitate the reabsorption of Na+ and secretion of K+
1. Na+ / K+ pumps on basolateral side pump three Na+ out into blood for every K+ pumped into the cell 2. This creates as low concentration of Na+ inside the cell 3. Na+ moves from the tubular fluid through Na+ channels in the apical side 4. Water is reabsorbed through Aquaporin molecule - normally found on the basolateral side, but number on apical side is increased by ADH

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