Tubular Transport- Proximal - Sheet1

Question 1

Transport in proximal tubule is driven primarily by? Located in what part of the cell?

Answer 1

Na K ATPase (maintains low intracellular Na for secondary active transport), basolateral

Question 2

Found in the basolateral and apical membranes of a proximal tubule renal cell?

Answer 2

Basolateral: Na K ATPase, Na channel (facilitated diff); Apical: Na H antiport (H goes out against gradient)

Question 3

How is bicarbonate reabsorbed?

Answer 3

Indirectly, by producing CO2 (carbonic acid -> [carbonic anhydrase] H2O + CO2); then may Na HCO3 cotransporter on the basolateral membrane

Question 4

Problems with bicarbonate reabsorption (NH3, NBC1) can manifest as? (2)

Answer 4

Metabolic acidosis, shock (hehe)

Question 5

Acetazolamide

Answer 5

Carbonic anhydrase inhibitor (diuretic)

Question 6

S3 function

Answer 6

NaCl paracellular reabsorption

Question 7

Na can be transported through secondary active transport via

Answer 7

Na H exchanger (antiport) & cotransport (symport) with glucose, aa, phosphate)

Question 8

Ouabain

Answer 8

Na K pump inhibitor

Question 9

In what part of the nephron are Na K pumps absent?

Answer 9

Descending limb (no Na reabsorption)

Question 10

How do kidneys deal with sodium load?

Answer 10

Excrete half the excess on the first day, remaining half the ff day, until equilibrium established

Question 11

(S1 & S2 vs. S3) Na glucose cotransporter & facilitative transporter

Answer 11

S1 & S2 (reabsorbs 90% of filtered glucose): SGLT2 (1:1), GLUT2; S3: SGLT1 (2 Na: 1 glucose), GLUT1

Question 12

Glucose transport is saturable up til what concentration? Presents as?

Answer 12

200 mg/100 ml; glucosuria

Question 13

Capacity & affinity of glucose carriers (S1 & S2 vs. S3)

Answer 13

S1 & S2 - high capacity, low affinity; S3 - low capacity, high affinity. No need for high capacity since there are fewer glucose molecules here, but high affinity needed to ensure all glucose is reabsorbed. :)

Question 14

Calcium transport (S1 vs. S2)

Answer 14

S1 - transcellular (needs pump); S2 - passive and paracellular (with Na & H2O)

Question 15

Effect of PTH on phosphate transport

Answer 15

Inhibits reabsorption, promotes excretion (stimulates endocytosis of NaPi2 cotransporters)

Question 16

Protein reabsorption how?

Answer 16

Endocytosis (active), lysed into aa inside the cell. (Amino acid reabsorption via a variety of Na-dep and Na-indep pumps….. basta yun ang sabi niya huhu.)

Question 17

Organic cations secreted via? (transporters)

Answer 17

Basolateral: Na K ATPase, OCT; Apical: OC-H antiport

Question 18

Endogenous cations secreted by proximal tubule (4)

Answer 18

Creatinine, dopamine, epinephrine, norepinephrine

Question 19

Drugs (cations) secreted by proximal tubule (7)

Answer 19

Atropine, isopoterenol, cimetidine, morphine, quinine, amiloride, procainamide

Question 20

Needed for organic anion secretion!

Answer 20

Alpha-ketoglutarate antiport (most drugs); some - basolateral simple & apical facilitated via MRP2

Question 21

Endogenous anions secreted by proximal tubule (6)

Answer 21

cAMP, bile salts, hippurates, oxalate, prostaglandins, urate

Question 22

Drugs (anions) secreted by proximal tubule (8)

Answer 22

Acetazolamide, chlorothiazide, furosemide, penicillin, probenecid, salicylate (aspirin), hydrochlorothiazide, bumetanide

Question 23

Significance of ammoniagenesis?

Answer 23

Acid-base balance – for generation of new bicarbonate and getting excess H+ (NH4+ excreted)

Question 24

Metabolic functions of the proximal tubule

Answer 24

Ammoniagenesis, gluconeogenesis, vitamin D synthesis

Question 25

Enzyme in proximal tubule for Vitamin D activation

Answer 25

1a-hydroxylase

Question 26

Which metabolic function of the proximal tubule is under hormonal control?

Answer 26

Vitamin D synthesis (PTH)

Question 27

Effect of decreased afferent and efferent resistance on reabsorption

Answer 27

Decrease reabsorption (low resistance -> dilation -> high capillary pressure -> low reabsorption)

Question 28

Effect of increased afferent oncotic pressure on reabsorption

Answer 28

Increase reabsorption (inc capillary oncotic pressure -> high reabsorption)

Question 29

Effect of increased Kf on reabsorption

Answer 29

Increase reabsorption

Question 30

How can angiotensin II increase reabsorption?

Answer 30

Vasoconstriction of efferent arteriole -> inc filtration fraction -> inc oncotic pressure -> inc reabsorption

Question 31

Adenosine - secreted by? Effect?

Answer 31

Granular cells; constrict afferent arterioles

Question 32

Major stimulus, nephron site of action, effect on transport: angiotensin II

Answer 32

Inc renin; PT, TAL, DT/CD; inc NaCl & H2O reabsorption

Question 33

Major stimulus, nephron site of action, effect on transport: aldosterone

Answer 33

Inc angiotensin II, inc plasma [K+]; TAL, DT/CD; inc NaCl & H2O reabsorption

Question 34

Major stimulus, nephron site of action, effect on transport: ANP, BNP, urodilatin

Answer 34

Inc extracellular fluid volume; CD; dec NaCl & H2O reabsorption

Question 35

Major stimulus, nephron site of action, effect on transport: uroguanylin, guanylin

Answer 35

Oral ingestion of NaCl; PT, CD; dec NaCl & H2O reabsorption

Question 36

Major stimulus, nephron site of action, effect on transport: sympathetic nerves (secrete other hormones)

Answer 36

Dec extracellular fluid volume; PT, TAL, DT/CD; inc NaCl & H2O reabsorption

Question 37

Major stimulus, nephron site of action, effect on transport: dopamine

Answer 37

Inc extracellular fluid volume; PT; dec NaCl & H2O reabsorption (so… it’s like ANP, except for site of action)

Question 38

Major stimulus, nephron site of action, effect on transport: ADH

Answer 38

Inc plasma osmolality, dec extracellular fluid volume; DT/CD; inc H2O reabsorption (so… not NaCl?)

Question 39

Why is the kidney an endocrine organ? (3)

Answer 39

Erythropoietin (peritubular endothelial cells/Lacis), renin (macula densa), calcitriol