Flashcards in Renal Phys--> Proximal tubule Deck (23):
How much filtrate is resorb in the proximal tubule?
- Total water resorbed is same as solutes
What else metabolically happens in the proximal tubules?
Vitamin D conversion
What gets handled in the proximal tubule?
3. Bicarbonate/acid secretion
6. phosphate resorb
7. weak organic acids resorption and polar substances
What are some things that increase the Na/H antiporter?
1. increased CO2
4. Decrease pH
What is the saturation point for SGLT2?
- synporter at proximal tubules
Where are the formate antiporters located? What is their purpose?
For Chloride resorption
- Late in the proximal tubule
- Enough Cl- has accumulated to have favorable conc. gradient
What would the lumen become after removing tons of Cl-?
- thus + charge molecules like Na+ are pushed out of the lumen (filtrate) through the paracellular space
What is carbonic anhydrase used for?
To combine H20 and Co2 to make H2Co3 and later H+ and Hco3-.
- found intracellularly
- found on brush border
how does bicarbonate get out of the cell?
Can water move paracellularly? If so how much?
How much Weak organic acid and bases does the proximal tubule handle?
- large filter load
- need to save most of the WOA
What are some examples of organic nutrients that you must not lose?
Water soluble vitamins
What are some endogenous cations that are secreted?
What are some endogenous anions that are secreted?
If WOAs and WOBs aren't absorbed in proximal tubule are they resorbed distally?
mostly secreted distally
How do neutral, negative and positively charged get into the cell?
Neutral and negative via synporter with Na+
- Positive via negative membrane gradient
- All share same transporters
Do we usually absorb polar substances?
-these are usually excreted
- liver usually metabolizes drugs to make polar which is both water soluble and is secreted!
what synporter do neutral and negative organic substances use?
Mono carboxylic acid
- into with Na and out of cell via diffusion
What are OCT's and OAT's?
How our body gets ride of drugs that are too big to be filtered. They are on the basolateral side and leave pericapillary. Then enter cell via this and leave cell into filtrate lumen via facilitated diffusion
B- hydroxybutyrate is found in the urine .What do you suspect?
- we are making tons of ketones and since our MCA's transporter has a Tmax (saturated), we can only absorb so much. Rest is excreted
Why would a drug need to use OCT and OAT to get out of body? Complications?
bond to albumin, thus too big to be filtered
- If to many drugs on board that use these transporters they will be longer acting if effects are in blood.
- They would be less efficient if effect is in tubules like Lasix... Thus you would need to increase dosage
What are some non-polar substances that are freely absorbed?