Renal Phys--> Proximal tubule Flashcards Preview

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Flashcards in Renal Phys--> Proximal tubule Deck (23):
1

How much filtrate is resorb in the proximal tubule?

60-70%
- Iso-osmotic
- Total water resorbed is same as solutes

2

What else metabolically happens in the proximal tubules?

Gluconeogenesis
Vitamin D conversion

3

What gets handled in the proximal tubule?

1. Na
2. Cl
3. Bicarbonate/acid secretion
4. Glucose
5. AA
6. phosphate resorb
7. weak organic acids resorption and polar substances

4

What are some things that increase the Na/H antiporter?

1. increased CO2
2. AGII
3. Sympathetics
4. Decrease pH

5

What is the saturation point for SGLT2?

15mM Glucose
- synporter at proximal tubules

6

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

7

What would the lumen become after removing tons of Cl-?

Slightly positive
- thus + charge molecules like Na+ are pushed out of the lumen (filtrate) through the paracellular space

8

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

9

how does bicarbonate get out of the cell?

Na/Hco3- synporter
1:3 ratio
Basallateral side

10

Can water move paracellularly? If so how much?

Yes
about 1/3

11

How much Weak organic acid and bases does the proximal tubule handle?

about 6mM
- large filter load
- need to save most of the WOA

12

What are some examples of organic nutrients that you must not lose?

Glucose
AA
Acetate
Water soluble vitamins
Lactate acetoacetate
B-hydroxybuterate

13

What are some endogenous cations that are secreted?

Creatinine
Dopamine
Epinephrine
Thiamine

14

What are some endogenous anions that are secreted?

Bile salts
Fatty acids
Oxalate
Prostaglandins

15

If WOAs and WOBs aren't absorbed in proximal tubule are they resorbed distally?

nope
mostly secreted distally

16

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

17

Do we usually absorb polar substances?

no
-these are usually excreted
- liver usually metabolizes drugs to make polar which is both water soluble and is secreted!

18

what synporter do neutral and negative organic substances use?

MCA
Mono carboxylic acid
- into with Na and out of cell via diffusion

19

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

20

B- hydroxybutyrate is found in the urine .What do you suspect?

DKA
- 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

21

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

22

What are some non-polar substances that are freely absorbed?

Steroids
Cholesterol
CO2

23

What causes resorption, in regards to hydrostatic and oncotic pressures?

Negative net pressure
- due to decrease in pressure due to increase resistance in peri-tubular capillaries