Tubular Transport III

Question 1

Rapid K regulation is accomplished by

Answer 1

rapid movement from IC to EC spaces through the action of Insulin, Epinephrine, and Aldosterone

Question 2

Which hormone can rapidly move K into cells?

Answer 2

Insulin: used to treat hyperkalemia

Question 3

Which hormone is used to move K out of cells? OR out of the cell?

Answer 3

Epinephrine + alpha-adrenoreceptors moves K OUT

Epinephrine + beta-2 adrenoreceptors moves K IN

Question 4

Which hormone promotes K uptake over hours?

Answer 4

Aldosterone: causes uptake of K INTO cells

Question 5

What would happen if there was chronic elevation of aldosterone?

Answer 5

Hypokalemia due to excretion of K and uptake of K into cells

Question 6

Where is K secreted if there is increased intake of K?

Answer 6

principal cell of distal tubule

Question 7

Where is K reabsorbed?

Answer 7

proximal tubule, loop of Henle, and INTERCALATED cells

Question 8

Main mechanism of K reabsorption in the proximal tubule?

Answer 8

solvent drag

Question 9

What are the primary physiologic regulators of K secretion in principal cells?

Answer 9

Plasma K and Aldosterone

Question 10

What else may alter K secretion?

Answer 10

Acid-Base balance and Tubular fluid flow rate

Question 11

Aldosterone causes Na reabsorption and therefore

Answer 11

K secretion; ENaC conductance increases, NA/K ATPase increases, K channels increased to secrete K

Question 12

ROMK channel

Answer 12

channel allowing passive diffusion on the apical membrane on the principal cell (gradient established by Na/K ATPase

Question 13

What factors determine K secretion?

Answer 13

Na/K ATPase function, electrochemical gradient driving force, permeability to K (ROMK)

Question 14

Aldosterone increases K secretion by:

Answer 14

increasing Na/K ATPases, increased Na reabsorption (increased ENaC through CAP1 and SGK1), increased # of ROMK channels

Question 15

Plasma K levels - hyperkalemia is corrected by

Answer 15

K secretion (aldosterone, increased Na/K ATPase, and permeability to K)

Question 16

Alkalosis has what effect on K secretion

Answer 16

INCREASES it via Na/K ATPase and ROMK; chronic alkalosis leads to hypokalemia

Question 17

Acute Acidosis has what effect on K secretion

Answer 17

DECREASES K secretion by inhibiting Na/K ATPase

Question 18

Chronic Acidosis has what effect of K secretion

Answer 18

INCREASES K secretion because aldosterone is stimulated

Question 19

How does an increase in tubular flow effect K secretion?

Answer 19

INCREASES K secretion

Question 20

How does a decrease in tubular flow effect K secretion?

Answer 20

DECREASES K secretion (hypovolemia)

Question 21

How does tubular flow rate change K secretion

Answer 21

Epithelial tubular cells have mechanosensor, when flow increases, Ca entry increases, and K channels open; why? because increased flow has increased Na –> Na reabsorption occurs and K secretion occurs

Question 22

Increased tubular flow rate causes ______ K secretion

Answer 22

Increases

Question 23

If we drink large amounts of water what happens to our K secretion?

Answer 23

stays the same, tubular flow rate is high but ADH is absent meaning low secretion of K

Question 24

Contradictory arguments for K secretion and tubular rate

Answer 24

Low ADH and high tubular flow (which can occur after ingestion of lg amounts of H2O), cancel each other out

Question 25

Liddle Syndrome (constitutively active ENaC)

Answer 25

High amounts of Na reabsorbed followed by H2O = hypertension, K secretion is high [hypokalemia] high BP and low RAAS

Question 26

Apparent Mineralcorticoid excess (AME)

Answer 26

licorice creates high levels of coritsol that mimics aldosterone; increased Na reabsorbed followed by H2O = hypertension, K secretion is high [hypokalemia] high BP and low RAAS

Question 27

Psuedohypoaldosteronism (loss of ENaC function)

Answer 27

decreased Na reabsorption, H2O loss, low BP, little secretion of K [hyperkalemia], increased aldosterone

Question 28

Bartter’s Syndrome (Na/K/Cl symporter loss of function)

Answer 28

large amounts of Na excreted (Na wasting), but Na is reabsorbed in the collecting duct and K is secreted in large amounts leading to [hypokalemia] increased RAAS

Question 29

Diuretics decreases ECF

Answer 29

by increased Na excretion, when ECF drops, RAAS is activated and Na reabsorption occurs elsewhere. ECF volume is established at a lower volume

Question 30

Naturiuresis

Answer 30

increase in Na excretion

Question 31

Kaliuresis

Answer 31

increase in K excretion

Question 32

Osmotic Diuretics act where and by?

Answer 32

proximal tubule; UNREABSORBABLE solutes cause retention of H2O in the tubule and therefore there is a decreased solvent drag (Na reabsorption) and increased Na back flow

Question 33

Example of osmotic diuretics

Answer 33

MANNITOL (large sugar); also diabetics with increased blood glucose experience this effect (polyuria, polydypsia)

Question 34

Carbonic Anhydrase inhibitor diuretic

Answer 34

prevents the production of H+ necessary for the Na/H+ antiporter in the proximal tubule therefore decreasing Na reabsorption

Question 35

Loop Diuretics

Answer 35

block the Na/K/Cl symporter in the thick ascending limb, this prevents the hypertonic medulla gradient from establishing and therefore reduced the ability of kidney to concentrate urine

Question 36

Example of a loop diuretic

Answer 36

furosemide (lasix)

Question 37

Thiazide diuretic

Answer 37

block the Na/Cl symport in the early distal tubule, decreasing Na reabsorption and decreasing the ability of the kidney to maximally dilute the urine

Question 38

K+ sparing diuretics

Answer 38

work in the late distal tubule and cortical collecting duct (therefore do not effect medulla gradient) to either block ENaC channels or act as an aldosterone inhibitor to prevent Na reabsorption

Question 39

Examples of K+ sparing diuretics

Answer 39

amiloride: blocks ENaC
Spironolactone: antagonizes aldosterone receptor

Question 40

Only group of Diuretics that does not waste K (vis increased K secretions)

Answer 40

K+ sparing in the distal tubule and collecting duct

Question 41

Only group of diuretics to not affect the ability of the kidney to maximally concentrate/dilute the urine

Answer 41

K+ sparing