Renal Flashcards
What are the 3 stimuli for renin release?
- Beta adrenergic stimulation
- Low sodium in the DCT (sensed by macula densa cells)
- Low renal arterial bp (sensed by JG cells)
What’s the equation for renal clearance?
CL=U*V/P
U=urine concentration of substance
V=urine flow rate
P=plasma concentration
How do we estimate GFR?
Clearance of inulin (UV/P)
What’s going on if the clearance of a substance is less than the GFR?
Substance is being reabsorbed by the tubules
What’s occurring if the clearance of a substance is more than the GFR
Substance is being secreted into the tubular lumen
What is a normal GFR?
~100ml/min
Does creatinine clearance overestimate or underestimate GFR?
Slightly overestimates GFR bc a little bit of creatinine is secreted from the tubules
What is PAH clearance used to estimate?
Renal plasma flow
CL of PAH
Why is PAH used to estimate RPF?
PAH is freely filtered and secreted.
All the PAH going to the kidney will be excreted!
What’s the equation for Filtration fraction?
FF=GFR/RPF
- GFR estimated with creatinine clearance
- RPF estimated with PAH clearance
What’s a normal FF?
20%
how do prostaglandins affect the GFR and RPF?
PG dilate the afferent arteriole, which will increase the RPF and GFR
What is the effect of NSAIDs on the GFR and RPF?
NSAIDs will block PG synthesis, leading to vasoconstriction of the afferent arteriole. This would decrease the GFR and RPF
Do NSAIDs affect the FF?
No, GFR and RPF are both decreased equally, so the FF would be the same
What is the effect of Angiotensin II on the glomerulus?
Angiotensin II preferentially constricts the Efferent arteriole. This creates a backpressure that will lead to increased GFR but decreased RPF (increased FF)
How do ACE inhibitors affect FF?
ACEIs inhibit the formation of AngT II, so this would lead to a vasodilation of the efferent arteriole. This would increase RPF but decrease GFR, leading to a Decreased FF
What’s the equation for filtered load of a substance?
FL=GFR*P
Equation for Excretion rate?
Excretion rate=U*V
How do you determine how much of a substance was reabsorbed?
filtered-excreted
How do you determine how much of a substance is secreted?
Excreted-filtered
Is glucose filtered?
Glucose and amino acids are freely filtered but reabsorbed by the renal tubules
How is glucose reabsorbed in the renal tubules?
Na/Glucose co-transporter in the PCT
How are amino acids reabsorbed?
Na cotransport
-There are separate transporters for neutral, positive and negative amino acids
Deficiency of transporter for neutral AAs. Leads to an inability to make niacin bc no tryptophan
Hartnup dz
inability to make niacin:
“3 D’s of pellagra”
-Dermatitis, Diarrhea, Dementia”
