Renal Tubular Function Flashcards
What is a normal plasma glucose
70-110
what classifies polyuria
> 2000 mL
what classifies oligouria
<500mL
what are the ways in which fluid and small solutes can cross the lumen barrier into interstitium to get to capillaries
paracellular via tight junctions
transcellular
What are the various mechanisms of transcellular solute transport
simple diffusion
facilitate diffusion (carriers down gradient)
primary active transport (ATP hydrolysis)
seconday active transport (co or counter-transport)
pinocytosis- protein reabsorption
What does the proximal tubule reabsorb
most filtered water, Na, K, cl, HCO3, Ca, phosphate and reabsorbs ALL filtered glucose, amino acids
what are secreted in proximal tubule
organic anions and cations like drugs and their metabolites, creatinine and urate
How come the osmolality never changes across tubule and plasma
because Na K and H2O are reabsorbed in equal quantities
How can you determine the amount of filtered water that is reabsorbed in prox tubule based on the TF/plasma [ ] ratio
look at the inulin concentration ratio
What does it suggest when PAH ratio is greater than the Inulin ratio on the T/F/plasma [ ] ratio
only secretion
How come the inulin ratio is high in the TF/plasma [ ] ratio
because 2/3 water leaving but inulin is not reabsorbed so gets greater concentrated after water leaves into plasma
describe the TF/P ratio of glucose in proximal tubule
becomes 0 because glucose is completely reabsorbed, more than water
Which way does the NaK pump work and why
pumps Na out of cell and brings K in.
this is so there is a gradient for Na to enter cell from lumen so it can:
co transport glucose
counter transport H+ ions
in loop of henle co transports with K and 2Cl
What is the mechanism causing reabsorption of urea and Cl
they become more concentrated because Na and H2O are leaving so the negative charges begin to repel eachother and drive themselves through the tight junctions into interstitium
What is responsible for moving the solutes in the interstitium into the capillaries
bulk flow and starling forces resulting in net reabsorption
what factors promote reabsorption in peritubular capillaries
high plasma colloid osmotic P
low hydrostatic P in capillaries
What organ regulates plasma [ ] of glucose and AA
the liver and endocrine system
By which mechanism is glucose and AA reabsorbed
secondary active transport, transcellular
how does glucose and AA exit the luminal cell into interstitium
facilitated diffusion
What limits the amount of glucose reabsorbed
number of Na glucose co transporters
How do you calculate filtration rate of glucose
GFR times the Plasma glucose levels
What is it called when there is glucose in the urine
glucosuria
What disease does the saturation of glucose occur
DM
what is tubular glucose maximum
rate of glucose reabsorption by all the nephrons combined
What can change the threshold value of glucose absorption
the number of transporters
why does urinary output increase in DM
becasue there is an increase of osmolarity in urinary filtrate so fluid will leave from plasma to try and normalize values
Osmotic diueresis
Why is a patient with DM thirsty
plasma osmolarity increase
What does an injection of mannitol do
it doesn not get reabsorbed so it sucks fluid into the lumen to decrease fluid levels in plasma.. used to decrease BP
Why do you see an increase of Na in a patient with DM diuresis
because Na follows H2O
What solutes utilize tertiary active transport and what is this
using 2 transporters to get out of intersititium
this is secretion of organic ions
what drugs exit via the tertiary active transport method
penicillin, salicylates(aspirin), antiviral drugs
Is PAH saturable
yes it can only secrete so much because # of transporters so the rest just goes through excretion
When the clearance of PAH, and Glucose plateau what does this mean
plateau at GFR because hit carrier maximum
what are secreted organic cations
catecholamines, acetylcholine and dopamine
what type of secretion method is used for organic cations
rely on Na/K ATPase gradient
then flow down via a diffusion carrier
what has to happen in order for organic cations and ions to be able to passively diffuse
need to be uncharged, less polar and more lipid soluble
When is a weak acid more nuetral
when protonated
when is a weak base more neutral
when deprotonated
Hydogen ions in the lumen favors diffusion of what organic compounds into plasma
acids
not bases- favors excretion
If a patient overdoses on aspirin how can you Tx
give patient bicarb so it stays in lumen and gets excreted
