Na & K Handling Flashcards
How is glucose reabsorbed in the proximal tubules?
By Na-dependent secondary active transport
How does glucose move?
Up against the concentration gradient from the lumen into the blood until concentration in the tubular fluid is 0
Where is the sodium glucose co-trasnporter located?
SGLT 2 is located only in the PT simultaneously transferring both Na and the specific organic molecule from the lumen into the cell
T/F: There’s a limited number of SGLT molecules present in cells lining tubules
True
What is the transport maximum?
Tubular maximum (Tm)
Any quantity of substance filtered beyond this isn’t reabsorbed and escapes into the urine (diabetes- defect in insulin)
Diabetes Mellitus
- Elevated plasma glucose levels
- Glucose freely filtered at glomerulus
- Glucose concentration exceeds the resorptive capacity of PT
- Glucosuria
Plyuria (osmotic diuesis)
Increased plasma osmolarity –> osmoreceptors in
hypothalamus –> polydipsia
What does the Na-K ATPase pump in basolateral membrane of the LH maintain?
A low intracellular sodium concentration and negative electrical potential in the cell
What is the role of the 1-Na, 2-Cl, 1-K co-transporter in the luminal membrane of the LH?
Transports those 3 ions from the tubular lumen into the cells, using the potential energy released by diffusion of Na down an electrochemical gradient into the cells
What does the Na-K ATPase pump in basolateral membrane of the distal tubule maintain?
A low intracellular Na concentration
What is the role of the Na-Cl co-transporter in the distal tubule?
Moves sodium chloride from the tubular lumen into the cell
Then chloride diffuses out of the cell into the renal interstitial fluid through channels
What inhibits 1-Na, 2-Cl, 1-K co-transporter?
Furosemide (diuretics)
This will inhibit the channel so no sodium will be released in the body, but it’ll be released in the urine taking water with in
Use this drug for high blood pressure
Loop Diuretics
Action: Inhibit Na+/K+/2Cl- cotransport in the thick ascending limb
Use: pulmonary edema, hypertension, heart failure
Agents: furosemide, bumetanide and torsemide
Thiazides
Action: Inhibit Na/Cl transport in distal tubule
Use: hypertension, heart failure
Agent: hydrochlorothiazide
K+ sparing
Action: aldosterone receptor antagonist Na+ channel inhibition in the cortical collecting duct
Use: Hypertension, supplement to loop or thiazide diuretics to reduce K+ wasting
Agents: spironolactone, amiloride, triameterene
Carbonic anhydrase inhibitors
Action: In PT and other organs expressing carbonic anhydrase
Use: heart failure (rare), loss of bicarbonate in urine (acute mountain sickness/ metabolic alkalosis), glaucoma (eye), epilepsy (CNS)
