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CRRAB II Week 2 > Proximal Tubule - Renal Physiology > Flashcards

Proximal Tubule - Renal Physiology Flashcards

1
Q

What happened in the case with the old lady taking NSAIDs and ACE inhibitor?

A

NSAIDs would block prostaglandins at the afferent arteriole.
This would vasoconstrict the afferent arteriole.
ACE inhibitors would block angiotensin II (vasoconstriction) at the efferent arteriole.
This would cause vasodilation of the efferent arteriole.
Overall, this causes dec. RPF (renal plasma flow), dec. pressure inside the glomerular capillary and dec. GFR (glomerular filtration rate)

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2
Q

How much does the kidney filter each day?

A

180L/day

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3
Q

What is the importance of the large kidney filtrate?

A
  • GFR is closely regulated (180L has a purpose)

- Filtered substances can be reabsorbed or secreted as needed to maintain homeostasis

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4
Q

Where is the proximal tubule located?

A

From the glomerulus to the Loop of Henle

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5
Q

How many capillary loops are there per glomerulus?

A

about 20

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6
Q

How much renal plasma flow goes into the glomerulus and how much goes out?

A

600 mls/min in

475 mls/min out

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7
Q

Where does the Efferent arteriole go after the glomerulus?

A

It branches off and follows/surroundings all tubules

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8
Q

How much blood is filtered in the nephron/minute?

A

125 ml/min

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9
Q

What is the order of tubules after the glomerulus?

A
  1. Proximal convoluted tubule
  2. Descending loop of henle
  3. Ascending loop of henle
  4. Distal convoluted tubule
  5. Collecting duct
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10
Q

In what direction does secretion go in the proximal tubule?

A

From peri-tubular capillary –> proximal tubule cell –> lumen

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11
Q

What is the lumen?

A

Where all the filtrate/urine goes (ureter)

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12
Q

In what direction does reabsorption go in the proximal tubule?

A

Reabsorption = things going from filtrate into peritubular space
From lumen –> proximal tubule cell –> peri-tubular capillary

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13
Q

If you don’t have functioning proximal tubule, what can’t you reclaim?

A

Phosphorus

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14
Q

How much of all filtered solutes and water are reabsorbed within the proximal tubule?

A

2/3

-This means wiping out the proximal tubule = trouble

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15
Q

What is the sum of total osmols reabsorbed proportional to?

A

Water! (iso-osmotic)

-300 mosoms

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16
Q

What are three mechanisms to move substances?

A
  1. Diffusion
  2. Channels
  3. Transporters
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17
Q

How does diffusion move substances?

A

Generally down a gradient. Primary method across peritubular capillary and paracellular.
-Non-charged substances (but much of what we filter is charged!)

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18
Q

How do channels move substances?

A

Facilitates diffusion across the lipid bi-layer

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19
Q

How do transporters move substances?

A

Generally slower than channels due to the tight binding of the substrate.

20
Q

What are two types of transporters?

A
  1. Uniporters

2. Multiporters

21
Q

What do uriporters transport?

A

Single solute movement

22
Q

What do multiporters transport?

A

Move 2 or more solutes simultaneously

-May move things in the same direction (symporter) or the opposite direction (anti-porter)

23
Q

What is active transport?

A
  • Can be done via a multi porter
  • Moves solute up its electrochemical gradient (ATPases)
  • –> Could be primary or secondary
24
Q

What is primary active transport?

A

Need to burn energy to make it happen

25
Q

What is secondary active transport?

A

One solute moves down its electrochemical gradient and this provides other solute energy to go against its electrochemical gradient.

26
Q

What is facilitated diffusion?

A

Getting help/escort transporting across bilayer

27
Q

What is the most prevalent “stuff” in your filtrate?

A

Na+ 140 mM

28
Q

What is the concentration of Na+ in the proximal tubule cell?

A

Na+ 4-10 mM

29
Q

What happens between the lumen and cell in terms of Na+?

A

Huge concentration gradient for Na+.

Na+ wants to get IN the cell!

30
Q

What is present on the basolateral side of the proxmial tubule?

A

Na+/K+ transport and its ACTIVE!

31
Q

What does the Na+K+ pump transport? What does it require? Where is it located?

A 
2K+ into the cell, 3 Na+ out of the cell (more positive pumped out than in)
Requires energy (luminal pump is passive)
Only basolateral/blood/anti-luminal side
32
Q

What is K+ doing in the proximal tubule cell, near the Na+/K+ ATPase?

A

K+ is recycling through the K+ channel

33
Q

Na+ is pumped ___ electrochemical gradient, out of cell.

A

UP

34
Q

The peritubular capillary has ______.

A

fenestrations

35
Q

What are Na-Glucose transporters known as? What ‘flavors’ do they come in?

A

SGLT (sodium-glucose linked transporters)

1 and 2

36
Q

What transporter reabsorbs 90% of glucose in the proximal tubule?

A

SGLT 2 (1:1)

37
Q

What sodium antiporter is located on the lumen side?

A

Na+ in, H+ out

38
Q

What three symporters are located on the lumenal side?

A

Na+, Glucose
Na+, Amino acids
Na+, PO4- (phosphorus)

39
Q

What four things regulate 2ndary active transport? What disease state are they present in?

A 
Inc. CO2
Inc. Angiotensin II
Inc. Sympathetics
Dec. pH
-Metabolic acidosis
40
Q

With Na+ Transport, glucose, amino acids and phosphorus are all being pumped UP their electrochemical gradient. What kind of transport is this?

A

Secondary Active Transport

41
Q

Normally, how much filtered glucose is reabsorbed in the proximal tubule?? MUST KNOW

A

100%

42
Q

What is the limit to the amount of glucose the proximal tubule can absorb?

A

Na+/glucose transporters have a saturation point/limit called the Transport Maximum (Tm).
-When this is reached, additional glucose will remain in the urine.

43
Q

When is the Tm reached?

A

At about 15 mM glucose

44
Q

What is 15 mM of glucose in the filtrate called?

A

Glucosuria = abnormal!

45
Q

Why can’t you use glycosuria as a test for diabetes mellitus?

A

Glucose in the urine is transport mediated so you could instead of DM have a genetic disease/proximal tubule disorder
–> Normal finger prick/serum glucose but glucose in urine

46
Q

What is the normal glucose level in the urine?

A

NONE

CRRAB II Week 2 (8 decks)

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