Tubular Transport Flashcards
What is the movement of solutes across the renal tubular epithelium between cells called?
Paracellular movement
What is the movement of solutes through the cells called?
Transcellular movement
What is involved in ‘active transport’?
Direct coupling of ATP hydrolysis to a transport process in the cell membrane - primary active transport
What is the most important primary active process in the nephron?
Na+/K+ ATPase
Where is the Na+/K+ ATPase located?
On the basal (and basolateral) side of the cells lining the nephron
What transporter accounts for much of the oxygen consumption of the kidney?
Na+/K+ ATPase
What are the other primary active transport mechanisms in the nephrons?
Ca2+ ATPase, H+ K+ ATPase
What is involved in ‘secondary active transport’?
Ionic gradients across the nephron cell membranes acting as driving forces for the reabsorption or secretion of many other solutes
What is the most important driving force for secondary active transport?
Sodium gradient
What are ENaC? Where are they located?
Epithelial Na Channel - located through out the nephron on the apical membrane of the cells
What drug closes the ENaC?
Amiloride
What proteins are tight junctions constructed of?
Occludin, claudins, junctional adhesion molecules
Is water reabsorption active or passive?
Passive
How does water movement occur in the nephron?
Water osmotically follows solute absorption
What channel allows reabsorption of water?
Aquaporins
Where are AQP-1 channels located?
Widely distributed in the body e.g. in lung and brain cells, and kidneys
Where are AQP-2 channels located?
In the collecting tubules
What is the incorporation of AQP-2 into the collecting tubule cell apical membranes controlled by?
ADH
Where are AQP-3 channels located?
In the basolateral membranes of the collecting tubule cells
What is the function of AQP-3?
Allows the cells to maintain homeostasis even when there is no AQP-2 incorporated in the apical membranes
When AQP-2 is installed in the apical membranes, AQP-3 allows water reabsorbed across the apical membrane via AQP-2 to leave the cells across the basal membrane and enter the interstitium
What is the process of water moving paracellularly, carrying some solutes with it?
Solvent drag
