diuretics

Question 1

what is oncotic pressure?

Answer 1

the presence of protein in a fluid that draws water in

Question 2

what transport occurs in the PCT?

Answer 2

facilitated diffusion of Na
diffusion of glucose and AA
Na/H exchange
HCO3-+ H+–> co2 +water (diffuses across)
paracellular diffusion of water and small ions

Question 3

what proportion of sodium is reabsorbed in the PCT?

Answer 3

65-70%

Question 4

describe what happens in the loop of henle

Answer 4

descending limb permeable to water, normal osmosis
no ion transport

ascending limb impermeable to water
Na/K exchanger (K in Na out)
K/Cl cotransporter (both out)
some diffusion of Cl- out

creates a counter current effect with a high osmotic pressure in the interstitium which pulls water out of the descending limb

Question 5

what transport do you get in the DCT?

Answer 5

ADH mediated aquaporins
K+/Cl- cotransport
Na/K exchanger
sodium channels

Na/cl cotransporter (tubule–> cell)

Question 6

what are the 5 main classes of diuretics?

Answer 6

osmotic diuretics
carbonic anhydrase inhibitors 
loop diuretics
thiazides 
potassium sparing diuretics

Question 7

give an example drug for :
loop diuretics
thiazides
potassium sparing diuretics

Answer 7

loop- furosemide
thiazide- bendroflumethiazide
k sparing- spironolactone

Question 8

what is the MOA of loop diuretics?

Answer 8

block the Na/Cl/K triple transporter protein (tubule–>cell)
this diminishes the ability of the ascending limb to increase the concentration of the interstitium and reduce the counter current effect

loop diuretics are strong diuretics (lots of water loss)

Question 9

what are the other effects of loop diuretics?

Answer 9

reduced excretion of sodium in ascending limb means that in the more distal part of the tubule sodium will try to be reabsorbed which can only happen at the expense of potassium so you get increased K loss

Question 10

where do thiazides act?

Answer 10

early distal tubule

Question 11

what is the MOA of thiazides?

Answer 11

blocks Na/Cl cotransporter

so less Na and Cl reabsorbed so less water reabsorbed

Question 12

how do you deal with the counter effect of the RAAS when giving diuretics?

Answer 12

usually pair with ACE inhibitors

Question 13

where do K sparing diuretics work?

Answer 13

end of the DCT

Question 14

what are the 2 classes of K sparing diuretics?

Answer 14

aldosterone receptor antagonist
eg. spironolactone

inhibitors of aldosterone-sensitive Na channels
eg. amiloride

Question 15

what is the MOA of aldosterone receptor antagonist?

Answer 15

blocks the action of aldosterone so less production of na channels and Na/K exchangers so less K lost

Question 16

what is the MOA of amiloride?

Answer 16

blocks the sodium channel so less Na in the cell to exchange for K

Question 17

what are the common side effects of loop diuretics and thiazides?

Answer 17

hypovolemia
metabolic alkalosis (Cl- ion loss)
hypokalemia
hyponatremia 
hyperuricemia (less uric acid excreted as uses the same transporter as diuretic so competing for use)
polyuria

Question 18

what are the side effects of K sparing drugs?

Answer 18

hyperkalemia

Question 19

what are the clinical uses for diuretics?

Answer 19

Heart failure- reduce the work load of the heart by reducing volume

activation of the RAAS causes cardicac remodelling which worsens HF

oedema(with HF)
if too much blood for heart to efficiently pump then will get pools in legs

hypertension