Diuretic effect on renin

[Pinkleton]

---

Members don't see this ad.

I need help remembering the effect of thiazides vs loops on renin...

I know that for loops, you have an increase in renin because the NaCl sensing transporter on the macula densa cells is the Na/K/2Cl transporter. So even though you have increased NaCl delivery, the kidney can't sense that so you have an increase in renin levels…

But with thiazides, this macula densa sensor would be left intact, right? So you would think that since the kidney can detect the increased NaCl delivery, thiazides should cause a drop in renin. But I've read that they also cause an increase in renin.

Can someone please clarify?? Thanks!!

 

[withrye]

I think the precise mechanism of sensing by the macula densa isn't particularly important for the purposes of the boards. Rather, the hypovolemia caused by diuretics is primarily responsible for the activation of the RAAS.

EDIT: It's possible to experimentally show a rise or blockade of renin following specific diuretic use by keeping the animal hyper/euvolemic, but we generally assume that patients undergoing diuretic treatment aren't being kept to these experimental conditions, but are rather experiencing a relative hypovolemia following treatment.

 

[Charles_Carmichael]

I think the precise mechanism of sensing by the macula densa isn't particularly important for the purposes of the boards. Rather, the hypovolemia caused by diuretics is primarily responsible for the activation of the RAAS.

Yea, that's how I think of it as well.

 

[Pinkleton]

Hmmm okay that makes sense. I thought that I learned something paradoxical on the topic, a while back...thought this was it haha. So loops and thiazides cause increased renin because of water loss...

What about after the initial diuresis period? Would you reach homeostasis and have a decrease of renin back to baseline?

 

[preDoGuy24]

I need help remembering the effect of thiazides vs loops on renin...

I know that for loops, you have an increase in renin because the NaCl sensing transporter on the macula densa cells is the Na/K/2Cl transporter. So even though you have increased NaCl delivery, the kidney can't sense that so you have an increase in renin levels…

But with thiazides, this macula densa sensor would be left intact, right? So you would think that since the kidney can detect the increased NaCl delivery, thiazides should cause a drop in renin. But I've read that they also cause an increase in renin.

Can someone please clarify?? Thanks!!

I didn't think the Na/K/2CL transporter was in the DCT? Maybe I just didn't study these details, but in this situation I think it's probably like everyone else has said a decrease in perfusion/volume mechanism, maybe even a reflex sympathetic discharge in there as well?

 

[Pinkleton]

I'm pretty sure that's right...I remember thinking it was weird because you have it in the loop of henle and all of the sudden in those specific cells in the distal tubule. I looked into it and withrye is right...giving an animal a loop plus saline still increases renin levels, which is not the case with thiazides. Not really clinically relevant I guess, because you guys are right about the baroreceptors activating the RAAS