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R5
Renal Handling of Organic Substances
27
Physiology
Professional
02/24/2013

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Cards

Term
What do we use PAH to measure? What do we have to remember to do in calculating this?
Definition

RPF; add 10% to final value because a small portion cannot be secreted

(90% of PAH is cleared on a single pass – 20% gets filtered and most of the rest gets secreted. 10% gets returned to the body. )
Term
Is the reabsorption of glucose and amino acids into the peritubular capillaries active or passive?
Definition
Active – it involves sodium-dependent secondary active transporters
Term
If 100% of glucose and amino acids are reabsorbed into the peritubular capillaries, how is this broken up along the nephron?
Definition
80% in proximal tubule; 20% in distal tubule
Term
What are the units for Tm (transport maximum)?
Definition
mg/min
Term
What three loads are plotted on the glucose handling curve? Which are linear until glucose reaches about 200 mg/dl?
Definition

Filtration, reabsorption and excretion

F and R are linear until 200 mg/dl

Term
What is the “splay region” on the glucose handling curve?
Definition
The region from 200 mg/dl (RPT) to 375 mg/dl where some glucose is being excreted but some is also being reabsorbed.
Term
What happens at 375 mg/dl on the glucose titration curve?
Definition
ALL of the glucose transporters are saturated
Term
What is the normal plasma glucose concentration on a 12 hour fast?
Definition
90-100 mg/glucose per dl
Term
What are most of the proteins that make up the 1.3-1.8 g/day of protein that is filtered?
Definition
Albumin, angiotensin, insulin
Term
How is albumin reabsorbed?
Definition
Pinocytosis in the proximal tubule
Term
How are angiotensin and insulin reabsorbed?
Definition
They are broken up into constituent amino acids and reabsorbed in total
Term
How and where do proteinaceous plugs form?
Definition
They are formed by proteins that filter through damaged glomerular filtration barriers and they form in the hairpin turn of the loop of Henle
Term
What direction of transport do organic anion transporters (OAT) and organic cation transporters (OCT) go in?
Definition
peritubular blood to proximal tubule = secretion
Term
Are OAT/OCTs passive or active?
Definition
They can be both – either facilitated diffusion (passive) or sodium-coupled secondary active transport (active)
Term
Is PAH a cation or anion? And is it endogenous or exogenous?
Definition
It is an exogenous organic anion
Term
How do inulin and PAH differ in measuring GFR?
Definition

Inulin is completely filtered and neither secreted nor reabsorbed.

PAH is partially filtered and not reabsorbed but the rest is secreted (there is usually about 10% left in the blood though).

Term
How does urate (base part of uric acid) react in the nephron?
Definition
It is partially secreted but preferentially reabsorbed in exchange for secreted anions
Term
Are bile salts, fatty acids, oxalates, prostaglandins, and urate anions or cations?
Definition
anions
Term
Are acetylcholine, choline, creatinine, dopamine, epinephrine, guanidine, histamine, serotonin, NE, and thiamine anions or cations?
Definition
cations
Term
What would result from acidification of the tubular lumen?
Definition

There would be an increase in the reabsorption of weak acids (HA) and an increase in the secretion of weak bases (B)

 

HA and B are more lipid soluble than A- and BH+

Term
Where is the proton concentration in the nephron the highest?
Definition
It is 1000x higher in the distal tubule than the rest of the nephron
Term
Is the proton pump located in the apical or basal membrane?
Definition
It is on the apical membrane between the tubular lumen and the renal tubular cells
Term
What is special about HA (undissociated/weak acids) and B (weak bases)?
Definition
They are lipid soluble and can be secreted/reabsorbed easily
Term
What is azotemia?
Definition
Elevated levels of nitrogen-containing compounds in the blood. It can be caused by uregenesis in the kidneys.
Term
What is the normal deep medullary osmotic gradient? What happens with tubular blockade by proteinacious gels?
Definition

1200 mosm/l

Tubular blockade destroys the medullary osmotic gradient and it takes 3 days to reestablish

Term
Where is the nephron urea impermeable?
Definition
Thick ascending loop of Henle, distal nephron, cortical collecting duct
Term
Where is urea secreted? Where is it reabsorbed?
Definition

secreted = thin loop of Henle

reasbsorbed = proximal tubule and medullary collecting duct

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