Lecture 38 Flashcards
Function of glmoerular filtration is where…
Selected components of the plasma are allowed to enter the bowman caopsule to the nephron (first step in urine formation)
Which portion of the nephron contributes most to the reclaiming of useful substances
Proximal convoluted tubule
Tubular reabsorbtion
Water and other useful substances are reclaimed by the kidneys tubules
Specialisations of the PCT
Microvilli - ↑ surface area
Fenestrated capillaries around PCT to aid exchange of substance
Reabsorbed molecules and how
Water - conc gradients
Urea - passive diffusion
Glucose- Glut2 transporters- facilitated diffusion trans cellular
Glucose also has SGLT-1+2 receptors (Sodium conc gradient)- active transport
Potassium sodium- primary active transport
SGLT1 and 2 relationship to GLUT1 and 2
SGLT1+2 move glucose across from filtrate into tubular cell
Glut1+2 move glucose from cell to blood
What limits the transport of glucose?
SGLT1 GLUT1
Too much glucose to reabsorbed through transporters = glucosuria eg diabetes
Disfunction of the SGLT1/2 receptors, due to drug inhibition
ONLY IN PCT
AMINO ACID REABSORPTION
PCT
Carried out by SLC (solute carrier proteins)
Aminoaciduria caused by
- high plasma AA (metabolic disease)
- disfunction of receptors (hartnup disease)
Reabsorption of sodium
Active transport transcellular
Secondary active transport (with glucose, AA or H+)
PCT initially
Further reabsorption in ascending loop via co transporters
DCT via co transporters
Benefit of sodium wasting and how
In times of hypertension or HF, this can ↓ BP by ↓ water levels in the blood
Sodium excretion = water loss via urine
Diuretics
- spironolactone =
prevents the effects of aldosterone ↓ sodium pump ↓ reabsorbtion
- loop diuretics
= inhibit co transporters in the ascending loop - thiazides
= inhibit co transporter in the DCT
Spironolactone use
Prevents sodium reabsorbtion by ↓ the effects of aldosterone on Na+/K+ pump expression which helps reabsorb sodium
Loop diuretics use
Inhibits the Na/Cl/K transporter in ascending loop
Thiazide Duirrtics use
Inhibits Na+/Cl- transporter in DCT
Water reabsorption
Movement across and through membranes as a result of the gradient produced by sodium
What facilitates water reabsorption
Aquapourins