2 Regulation of Renal Hemodynamics

Question 1

Why do kidneys receive 20% of cardiac output?

Answer 1

Need to make a high amount of ultrafiltrate.

Question 2

Explain the relationship between renal blood flow (RBF) and O2 consumption

Answer 2

Renal O2 demand is actually BASED ON FLOW (inverse of all other tissues).
—Major O2 user is active transporters involved in reabsorption
—very little A-V ∆O2

Question 3

Where is epo produced? Why?

Answer 3

The renal cortex

“The result of this unusual coupling is that renal A-V ΔO2 and thus tissue pO2 are independent of blood flow. Consequently, the key determinant of tissue pO2 is arterial O2 content.”

Question 4

Explain how the dynamics of ultrafiltration and reabsorption in the kidney
differs from those in other organs.

Answer 4

In “normal” vasculature, low ultrafiltration due to hydrostatic force
—90% is then reabs. due to oncotic pressure more distally in the capillary; the remaining ~10% is taken away by the lymph sys

In the kidney:
—two capillary sys in SERIES
—much higher filtration coefficient creating high amounts of ultra-filtrate that is modified by active transport of different solutes

Question 5

Describe the consequences of changes in afferent and efferent arteriolar
resistances on RBF, GFR and on the Starling forces in peritubular capillaries.

Answer 5

?

Question 6

What is the equation for GFR

Answer 6

GRF = (P[cap]-P[bs]) - onc. P[cap]
—can ignore Kf because it is so high (~1)
—onc. P[bs] should be zero

Question 7

What are the layers of the filtration barrier?

Answer 7

1. MAIN: thick, multilayered basal lamina (molecular sieve)
2. slit diaphragm, extended between the foot processes of the podocytes
3. glycocalyx filling fenestrations of the glomerular endothelium

Question 8

What is the charge of the filtration barrier? Which layers are charged?

Answer 8

NEGATIVE

—all layers are charged

Question 9

What are the two major proteins in the blood?

Answer 9

albumin and Ig

Question 10

How does an increase in RBF ∆ onc. P[cap]?

Answer 10

lowers it

Question 11

What is the main determinant of GFR?

Answer 11

P[gc]

—”pressure of glomerular capillary”

Question 12

How does P[cg] ∆in relation to Aff tone? Eff tone?

Answer 12

It ∆s in parallel with Aff tone and opposite of Eff tone

Question 13

What’s the charge on albumin?

Answer 13

NEGATIVE

Question 14

What is minimal charge nephropathy?

Answer 14

dz of childhood in which the glom. filter loses charge.

Question 15

What are the f(x)s of the peritubular capillaries?

Answer 15

1. nourishes tubules

2. return reabsorbed fluid and solutes to central circulation

Question 16

Where are the AA and EA in relation to the glom cap network and the peritubular cap network?

Answer 16

AA—g.c. network—EA—peritub. caps

Question 17

How is it that peritubular capillaries are able to reabsorb fluid?

Answer 17

—they have a decr. (outward) hydrostatic pressure

—they have an incr. (inward) hydrostatic pressure

Question 18

What is used to estimated clearance? Why?

Answer 18

PAH—para-aminohippuric acid

—used b/c PAH is actively secreted to the point that ~100% is cleared in one pass

Question 19

What is used to estimated GFR?

Answer 19

inulin, though not all is cleared, so it’s an analog for GFR

—clinically: more often use creatinine

Question 20

What is the equation for renal clearance?

Answer 20

conc of substance in urine X urine flow (V)

OVER

conc of substance in arterial plasma

Question 21

Describe the neurohormonal regulation of RBF and GFR.

Answer 21

?

Question 22

What is the effect of Effect of dilation of the afferent arteriole on RBF and GFR

Answer 22

?