ACE Inhibitors - why do they want to increase renin? HELP, please!

[Aim2Nurse]

Hello Nursing Community! I'm a new student and I came across something that is driving me crazy if someone can please answer and help!

Reading on ACE Inhibitors describes how they work, which I understand how they work on Ang II, however, the drug guide book also states, "ACE inhibitors also ↑ plasma renin levels and ↓ aldosterone levels. Net result is systemic vasodilation." Why would an antihypertensive therapeutically work to INCREASE renin? I suppose negative feedback would result in ↑ plasma renin, but the drug guides state this as a therapeutic action. I can't understand this for the life of me. Please someone, help! Help! Ive been looking this up online all night last night.

[LR_C]

Hey! I wouldn't for the life of me be able to translate my understanding in my head to words so I'll copy what my "Clinical Pharmacology Made Incredibly Easy" book explains regarding ACE inhibitors because I totally understand what you're saying but I think that this explains it well. Let me know if you still don't get it after I send you this.

ACE inhibitors reduce BP by interrupting the renin-angiotensin-aldosterone system. Normally, the kidneys maintain BP by releasing the hormone renin. Renin acts on the plasma protein angiotensinogen to form angiotensin I. Angiotensin I is converted to Angiotensin II (potent vasoconstrictor) which increases peripheral resistance and promotes the excretion of aldosterone. Aldosterone> promotes retention of sodium and H20> blood volume increases

BUT! ACE inhibitors prevent the conversion of angiotensin I to angiotensin II> angiotensin II is reduced> arterioles dilate> peripheral vascular resistance decreases

By reducing aldosterone secretion, ACE inhibitors promote the excretion of sodium and water, which reduces the amount of blood the heart needs to pump> BP is lowered

I really hope that helped!

[Aim2Nurse]

Hi, Yes that makes sense and may I add it's quite easy to understand. I've heard of that book....I may have to try it out now. I still don't get the renin increase thing though. I can't find anything that explains the therapeutic revelance of increasing renin. Blah. Frustrating. Thanks so much though for this info and the book rec.:)

[2ndyearstudent, CNA]

The renin is released for a reason. If you interrupt the process that might inhibit release of renin (RAA), it will continue to be released, increasing plasma levels.

It would be nice if ACE inhibitors also supressed the release of renin, but they don't.

Many of my classmates have problems with stuff like this. It is important to distinguish between what the physiologic processes do and what you would like them to do. They don't always agree.

[Mike R, ADN, BSN, RN]

Whoops, double post.

[Mike R, ADN, BSN, RN]

I still don't get the renin increase thing though. I can't find anything that explains the therapeutic revelance of increasing renin.

I don't know which Drug book you're using, but the spiel about increasing Renin levels in my Davis book is under "Actions" and the sentence just before "therapeutic effects"; not to be included as a therapeutic effect.

It's not therapeutic per-say, just a negative response to a stimuli like you said.