Renal Hemodynamics: Things I don't Know

Question 1

What is the function of a Slit Diaphragm and what is it composed of?

Answer 1

The Slit Diaphragm functions as a Size-selective filter.
It is composed of:
Nephrin, NEPH1,2,3, Podocin, CD2-AP, alpha Actinin

Question 2

What kind of substances CANNOT pass through the GC endothelial cells?

Answer 2

Size: Molecules > 70,000 Daltons MW
Charge: Extremely (-) charged molecules

Question 3

Why can’t Negatively charge ions pass thru the GC endothelial cells?

Answer 3

Because the Filtration Barrier is coated with Polyanions which tend to repel (-) charges

Question 4

What physical characteristics of the GC endothelial cells regulate Filtration?

Answer 4

1) The size of the space btw Endothelial cells
2) The size of the space btw Podocytes of Bowman’s Capsule

They act like 2 strainers put together

Question 5

What is the order in which filtrate travels within the Glomerulus?

Answer 5

1. Fenestrae in GC endothelial Layer
2. Basement Membrane
3. Slit Diaphragms btw podocyte processes (size-selective barrier)

Question 6

What factors determine Permeability?

Answer 6

1) The size of the space btw GC endothelial cells

2) The size of the space btw Bowman’s Capsule Podocytes

Question 7

What factors determine Surface Area?

Answer 7

1) Mesangial cell status

2) # of Viable Nephrons

Question 8

What is the formula for Osmolarity?

Answer 8

Osmolarity = [ concentration] x # of dissociable particles 
mOsm/L = mmol/L x #/mol

Question 9

What happens when you inhibit Carbonic Anhydrase?

Answer 9

You will increase Bicarbonate Excretion
Decrease Na+ Reabsorption and Increase Na+ Excretion
* remember that Reabsorption of Bicarbonate is coupled to Na+ reabsorption*