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Renal Physiology > Ch.4/5 GFR,Prox,Henle > Flashcards

Ch.4/5 GFR,Prox,Henle Flashcards

1
Q

Review: What are the 3 principle components of renal function?

A

GFR, Reabsorption, Secretion

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2
Q

What is PAH used to measure? Why?

A

Para-Amino-HippUric Acid is used to measure RPF..because it is freely filtered and avidly secreted for total excretion

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3
Q

What can you use to measure RPF?

A

PAH-freely filtered and fully secreted=total exctretion

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4
Q

What are examples of substances that are more reabsorbed then excreted?

A

Na+,Cl-, H2O

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5
Q

What are two examples of a substance that is filtered but then completely reabsorbed and NOTHING is excreted?

A

Glucose, Bicarb

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6
Q

What is the general trend of all the substances listed and their amount reabsorbed? (There was only one substance that didn’t fit in…what was it?)

A

Most of the substances were MOSTLY reabsorbed back into the body (H2O=99.2%, Na+=99.4%…) The only odd ball was Urea=50% reabsorption (thank God! were getting rid of it!)

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7
Q

What is transport from the Lumen of the Nephron to the Peritubular Capillary called? Which ends of the nephron participate?

A

Tubular Reabsorption…BOTH the Proximal and Distal ends of the Nephron participate in this.

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8
Q

What is transport from the peritubular capillaries to the Lumen of the Nephron? Which ends of the nephron participate?

A

Tubular Secretion…ONLY in the PROXIMAL tubules

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9
Q

What are the 2 ways transport can occur across the renal epithelial cells? Which one is the major way?

A
  1. Transcellular (majority) 2.Paracellular
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10
Q

What are the 3 trans-membrane transport systems at work?

A

1.Channel-Mediated diffusion (passive, uses [gradient])…2.Carrier Mediated diffusion (uniport, symport, anti port)…..3.Carrier-Mediated ‘active transport’ (ATP needed, against [gradient])

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11
Q

Absolute dependence on Na+-K+-ATPase located ONLY on the _______ membrane to maintain low intracellular ____ concentration.

A

basolateral…[Na+]

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12
Q

Where does Na+ enter the cell via luminal membrane Na+-selective channels?

A

The Cortical COLLECTING TUBULE

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13
Q

Where am I?(area of nephron and which membrane) Downhill” movement of Na+ across luminal membrane into the cell facilitates “uphill” movement of glucose

A

Proximal Tubule…Luminal Membrane

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14
Q

Where am I?(area of nephron and which membrane) … Glucose uniporter transports glucose out of the cell across the basolateral membrane

A

Proximal Tubule…Basolateral Membrane

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15
Q

What are the two Co-Transporters on the luminal membrane of the proximal tubule that transport Na+&Glucose?

A

SGLT-2 (high capacity-low affinity) & SGLT-1 (low capacity-high affinity)

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16
Q

What do type II DM patients use SGLT-2 inhibitors?

A

To keep Glucose out of the blood and excrete it into the urine. If they block these SGLT-2’s in the proximal tubule, they won’t reabsorb as much.

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17
Q

How do the 7 types of Na+ transporters of the Proximal tubule get categorized?

A

3 Amino Acid cotransporters, 2 phosphate co-transporters, 1 Na+-H+ exchanger and 1 Neutral/dibasic(cationic)/dicarboxylic(anionic)

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18
Q

For the 10% of protein that does sneak by and get filtered (OH and Vit-D as well)…What are the two binders and what is the area the protein is brought into the cell?

A

Megalin & Cubulin bind and then into membrane Clathrin-Coated Pits (CCP)

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19
Q

What happens to those sneaky filtered proteins once they’ve been endocytosed? (and Vit-D!)

A

Degraded to AA’s and released basolaterally..then randomly Vit-D gets activated

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20
Q

About how much glomerular filtrate is reabsorbed in the proximal tubule? What are the examples of H2O and Na+?

A

Approx 2/3…H2O 180L–>120L and 26,000mEq of Na+–>17,000mEq

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21
Q

Which solutes are COMPLETELY absorbed proximally?

A

Glucose, AA’s, HCO3-

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22
Q

What 2 things are unique about the reabsorption of Cl- in the proximal tube?

A

It happens much later then the other substances AND its absorbed paracellularly!

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23
Q

What is the 2 step process for the REST of absorption (after the initial 2/3 in the proximal tubule)?

A

1.Small osmotic gradient is made (tubular fluid osmolality < extracellular fluid) 2.Water moves from the lumen to the intersitium down its osmotic gradient

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24
Q

Complete reabsorption of this isotonic fluid from the proximal tubule is a two-phase process…What are they? What drives the second phase?

A

1.lumen —> interstitium 2.Interstitium—>peritubular capillaries DRIVEN by Starling Forces

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25
Q

Which two starling forces regulate peritubular capillary fluid uptake?

A

LOW Peritubular Capillary HYDROSTATIC pressure (downstream of the afferent/efferent resistance points) AND high oncotic pressure (high [protein])

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26
Q

The proximal tubule reabsorbs a constant percentage (~67%) of the filtered load: so-called _________.

A

GLOMERULOTUBULAR (GT) BALANCE

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27
Q

GT balance helps maintain a relatively constant delivery of fluid to the _______.

A

Distal nephron

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28
Q

If GFR is 100ml/min how much will make it to the Loop of Henle?

A

33ml/min = (100-(2/3x100)) 2/3 of GFR taken reabsorbed by this proximal tubule!

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29
Q

What happens to proximal tubule reabsorption when we increase efferent arteriolar resistance?

A

Increase in Efferent Arteriole Resistance = Increase in P in the GC = Increase in GFR = INCREASE in proximal reabsorption (WHA??)

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30
Q

What is the filtration fraction?

A

Filtration Fraction= (GFR/RPF)

31
Q

When collecting samples via IN VIVO micropuncture, what areas can you access? What areas can’t you?

A

Can get the Proximal and Distal Tubules…Cannot get to juxtamedullary nor collecting tubule

32
Q

If we use micro puncture in vivo, what do we use in vitro?

A

Microperfusion…cut out any portion of the Kidney you want to sample and run stuff through it.

33
Q

What is the point where all transport proteins are saturated in the tubule??

A

Tubular Transport Maximum (Tm)

34
Q

How do I find the amount of a material that is Reabsorbed?

A

Amount Reabsorbed=Amount Filtered- Amount Excreted

35
Q

How do I find the amount filtered?

A

Amount Filtered = GFR x Particles of Glucose

36
Q

How do I find amount excreted?

A

Amount excreted = Volume x Urine Glucose

37
Q

“_____”- represents the slight variance in Tm between individual nephrons.

A

“Splay”–some nephrons have LOTS of SGLT-2s some have less..

38
Q

“_______”- represents the plasma concentration (of glucose) at which Tm is exceeded.

A

“Threshold”

39
Q

Why is there Glucose in the pee of DM Patients?

A

filtered load of glucose has become&raquo_space;> than TubularTransportMaximum (Tm)

40
Q

What is the primary site of secretion for organic anions and cations?

A

The proximal tubule!

41
Q

What are the two Exogenous Anions used as “Loop Diuretics”? (they are not filtered well, but secreted)

A

Fur-os-em-ide & Bum-et-an-ide

42
Q

What are the 3 transporters involved in Organic Anion(OA) transport across the Basolateral membrane? CAN YOU DRAW WHATS HAPPENING?

A

1.Organic Anion Transporters 1 & 3 (OAT-1 & OAT-3) 2.Na+-Dicarboxylate Cotransporter (NaDC) 3.Na+/K+ pump

43
Q

Organic Anions are taken up across the ________ in exchange for_________ via Organic Anion Transporters 1 and 3 (OAT-1; OAT-3).

A

basolateral membrane…. α-ketoglutarate (αKG)

44
Q

In organic anion transport in the Proximal tubule::: effluxed _______ is taken back into the cell via Na+-dicarboxylate cotransporter (NaDC).

A

α-ketoglutarate (αKG)

45
Q

What are the two transporters that take Organic Anions across the Luminal Membrane? WOW! freaking lots of action to get these Organic Anions secreted into the Urine!!

A

OAT-4 and Multidrug Resistance-associated Protein-2 (MRP-2)

46
Q

What atet the 4 pumps involved in the secretion of Organic Cations? (break them down by which membrane please)

A

Basolateral:Na+/K+ pump & OCT-1,2,3………Luminal:OC-H+ Antiporters (OCTN) and MDR1 (p-glycoprotein)

47
Q

How do we use OAT’s non-selective behavior to our advantage during administration of penicillin?

A

Giving PAH with Penicillin keeps the OAT’s from secreting the Penicillin. (OATs will move either)

48
Q

What are the two stipulations for a GFR marker?

A

1.Never Reabsorbed nor Secreted 2.Not produced or metabolized by the kidney

49
Q

What are the two primary GFR markers? How will I find GFR if by knowing excretion?

A

Inulin and creatinine…Since Inulin and Creatinine are freely filtered and NOT reabsorbed nor secreted, GFR=excreterd GFR=Vol x Urine Inulin / Inulin in

50
Q

For inulin or creatinine, ALL of the plasma filtered by the glomeruli is effectively “_______” .

A

“cleared”……Hence the clearance of inulin (CIN) or the clearance of creatinine (CCR) = GFR

51
Q

Simultaneously measuring the clearance of substance X and the clearance of inulin or creatinine can provide an indication of how X is handled by the kidney: When CX

A

reabsorption

52
Q

Simultaneously measuring the clearance of substance X and the clearance of inulin or creatinine can provide an indication of how X is handled by the kidney: When CX > CIN the substance must undergo net _______.

A

secretion

53
Q

What substances have a clearance of 0?

A

Glucose, Bicarb (when things are working normally)

54
Q

How are we to find RPF??

A

X amount in (renal artery) = X amount out (renal vein) + X amount out (urine)…1) RPF=Urine PAH x Vol / P PAH 2)

55
Q

How do I find RBF??

A

RBF=RPF/(1-hematocrit)

56
Q

Interstitial osmolarity progressively ________ from cortex / medulla border to papilla tip.

A

increases

57
Q

Cortex interstitial osmolarity: _____ mOsm/L (isotonic)

ii. medulla interstitial osmolarity gradient in humans: ____—> _____ mOsm/L (cortical junction —> papilla tip).

A

300 mOsm/L….300—>1400mOsm/L

58
Q

Hypertonicity created by deposition of ____ and ____ into medulla interstitial. This interstitial hypertonicity is essential for __________.

A

NaCl and urea….. urine concentration

59
Q

Humans can excrete a urine with an osmolarity of ____ mOsm/L; rats, a urine of _____ mOsm/L)

A

1400 mOsm/L……3000mOsm/L

60
Q

What are the two functions of the descending limb of Henle’s Loop?? (makes sense!)

A
  1. REABSORB H2O 2.NO SOLUTE REABSORPTION (especially NaCl!)…makes sense because we are gaining osmolality as we go down the loop
61
Q

ThinDescendingLimb system capable of reabsorbing approx __ - ___ L H2O/day!

A

30-40L H2O/day!

62
Q

What are the main 2 functions of the Ascending limb of Henle?

A
  1. AVID Reabsorption of NaCl (we have to get the osmolality of the surrounding area back down to 300) 2. NO reabsorption of H20 (same logic as above)
63
Q

What is the nickname for the ascending loop of henle?

A

“the diluting segment”

64
Q

What transporter is on the BasoLateral membrane of the thick ascending limb? (think of function!)

A

Na+/K+ pumps present on BL surface (we are AVIDLY reabsorbing NaCl) This will help us kick Na+ out

65
Q

Which transporter is on the Luminal membrane of the thick ascending limb? (Think of overall function!)

A

We need to pull NaCl out of the Lumen for AVID reabsorption…so…An Na+-K+-2Cl- co-transporter is used here

66
Q

Thick ascending limb: HOW IN THE WORLD do we get the necessary K+ out of the cell, into the luminal space, and then BACK into the cell to help other solutes out?

A

A K+ selective channel helps K+ go down its [gradient] out of the cell. This will then do 2 things. 1. Make a Positive Extra cellular environment for paracellular transport of cations…2.supplies our Na+-K+-2Cl- co-transporter

67
Q

What transporter is blocked by LOOP DIURETICS?

A

Na+/K+/2Cl- transporter

68
Q

What does ADH do to transportation in the thick ascending limb?

A

Increases transport (NaCl reabsorption)

69
Q

What does Anti Natriuretic Peptide do to transportation in the thick ascending limb?

A

Inhibits transport

70
Q

WHERE does Bartter’s syndrome have an effect?

A

The thick ascending limb

71
Q

Where is K+ funky efflux happening?

A

Thick ascending limb

72
Q

How would you describe the reabsorption of NaCl in the thin ascending limb?

A

Passive and limited…WEAK SAUCE

73
Q

WHY is NaCl PASSIVELY absorbed along its gradient at the bottom of the L of H?

A

cause like the Tubular Fluid is 80% NaCl compared to the Interstital fluid of 50% NaCl (THANKS to 50% urea)

Renal Physiology (5 decks)

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