Renal Tubules Transport Mechanisms Flashcards
What are the three methods of passive transport that occurs in the kidneys?
Diffusion
Osmosis
Electrochemical gradients
What are the two types of active transport which occurs in the Kidneys?
Primary Active Transport and Secondary Active Transport
How is endocytosis used in the renal tubules?
Small proteins are reabsorbed in the proximal convoluted tubules
What is an example of a symporter?
The Na+ / Glucose Symporter
How do symporters and antiporters provide methods of secondary active transport?
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
Describe how Na+ / K+ ATPase Pumps work?
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
How does the presence of Na + / K+ ATPase Pumps on the basolateral membrane help the transportation of other substances?
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
Describe the reabsorption of sodium in the Early Proximal Convoluted Tubule?
- Na+ / K+ ATPase Pump creates low Na+ inside cell
- 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
- Then Na+ moves through Na+ / HCO3- Symporter on Basolateral side into blood
Describe the reabsoprtion of HCO3- in the early proximal convoluted tubule
- Na+ / K+ ATPase Pump creates low Na+ inside cell
- Carbonic Anhydrase converts water and co2 into H+ and HCO3-
- Na+ moves through Na+ / H+ Anti Porter on Apical Side into the cell, as H+ moves into tubular fluid
- Then Na+ and HCO3- move through Na+ / HCO3- Symporter on Basolateral side into blood
How does Angiotensin II regulate Na+ reabsorption in the Early Proximal Convoluted tubule?
By Increasing the number of Na+ / H+ Antiporters
What happens to sodium, bicarbonate and glucose in the Early Proximal CT?
Sodium - Reabsorbed
Bicarbonate - Reabsorbed
Glucose - Reabsorbed
Describe the reabsorption of glucose into the Blood in the Early Proximal Convoluted Tubule?
- Na+ / K+ ATPase Pump creates low Na+ inside cell
- Na+ and glucose from tubular fluid moves through Na+ / Glucose Symporter on Apical Side
- Then glucose moves through GLUT2 transporter on the basolateral side into the blood
What is the name of the Na+ / H+ Antiporter found on the apical side of the Early Proximal Convoluted Tubule?
NHE3
What is the name of the Na+ / Glucose Symporter found on the apical side of the Early Proximal Convoluted Tubule?
SGLT2
What percentage of glucose is reabsorbed in the Early Proximal Convoluted tubule
100%
What percentage of Water, Na+ and Cl- are reabsorbed in the Early Proximal Convoluted Tubule?
67% Water
67% Na+
67% Cl-
What percentage of amino acids are reabsorbed in the early Proximal Convoluted tubule?
100%
What percentage of bicarbonate is reabsorbed in the Early Proximal Convoluted Tubule?
80%
What substances are secreted in the Early Proximal Convoluted Tubule?
Drugs, Ammonia, Bile Salts, Prostaglandins, Vitamins
What is the osmolarity of the fluid entering the LOH?
Isosmotic
Is Na+ Cl+ reabsorbed in the descending LOH?
No