Adenosine - vasodilator or vasoconstrictor?

[Phloston]

The internet seems to say a million different things.

It's to my understanding that adenosine always decreases cAMP via G-alpha-i, meaning that it causes vasodilation of coronary arteries, but vasoconstriction of arterioles elsewhere in the body, including those of the bronchiolar smooth muscles and arterioles of the kidney.

In other words, if I have it correct, adenosine causes bronchoconstriction and decreased renal perfusion via vasoconstriction, but increased coronary blood flow via vasodilation.

I've also read that caffeine blocks adenosine receptors in the brain, leading to vasodilation, so I've assumed adenosine causes vasoconstriction pretty much everywhere except for the heart.

Is that right or am I missing something here? As far as what you guys know, what is the action of adenosine, both in general and at specific locations?

Cheers,

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[Brotato]

I thought metabolites like adenosine/CO2/etc caused vasodilation everywhere except the lungs (because the lung responds to hypoxia by vasocontricting)?

 

[Charles_Carmichael]

From what I've learned, adenosine causes vasodilation in most organs. The main organ where I think of adenosine and vasoconstriction is the afferent arteriole in the kidney -- I believe there's some evidence suggesting adenosine plays a role in tubuloglomerular feedback.

Organ-specific, I know adenosine is important in vasodilation of coronary vessels, particularly during hypoxic situations or when cardiac metabolism increases. For cerebral vasculature, I generally think of pCO2 mainly influencing vasodilation/vasoconstriction; haven't head too much about adenosine there, but it would make sense that it's a vasodilator (considering the importance of metabolism in regulating cerebral blood flow). For pulmonary circulation, I thought the hypoxic vasoconstriction was thought to be mediated via ET, ROS, Ca2+, etc, and not-so-much adenosine? So, I'm not entirely sure how much of a role adenosine plays there. Renal circulation --- going back to the TGF. Never really heard/read anything about adenosine playing an important role in regulating splanchnic circulation.

Like I said, the main (only?) thing I generally think of when adenosine and vasoconstriction comes up is in the renal circulation. But, I'm only a rising M2, so take that with a grain of salt.

Hope that helps.

 

[MrBeauregard]

Like I said, the main (only?) thing I generally think of when adenosine and vasoconstriction comes up is in the renal circulation. But, I'm only a rising M2, so take that with a grain of salt.

Adenosine is also the main regulator of arteriolar blood flow in the coronary arteries in response to increasing cardiac workload.

 

[Charles_Carmichael]

Adenosine is also the main regulator of arteriolar blood flow in the coronary arteries in response to increasing cardiac workload.

Right, I mentioned that in my prior post. In the sentence you quoted, I meant that the renal circulation is what I think of when I think of adneosine primarily acting as a vasoconstrictor. My bad if that wasn't clear. 🙂

 

[MrBeauregard]

Right, I mentioned that in my prior post. In the sentence you quoted, I meant that the renal circulation is what I think of when I think of adneosine primarily acting as a vasoconstrictor. My bad if that wasn't clear. 🙂

Oh actually I just completely misread. My bad.

 

[Phloston]

My guess is that adenosine has to cause vasoconstriction at the lungs because theophylline, a vasodilator, blocks the action of adenosine.

Btw, I had written this thread before I went to sleep and, while sleeping, realized that FA mentions adenosine as a main regulator (along with K+ and lactate) of skeletal muscle blood flow.

Since beta-2 increases blood flow through the skeletal muscle and also increases cAMP, given that adenosine always decreases cAMP means that adenosine must cause vasoconstriction at the skeletal muscle.

I'd hope I'm getting my facts straight before jumping to conclusions like this.

Anyone else's thoughts on any of this stuff?

 

[Aclamity]

My guess is that adenosine has to cause vasoconstriction at the lungs because theophylline, a vasodilator, blocks the action of adenosine.

Btw, I had written this thread before I went to sleep and, while sleeping, realized that FA mentions adenosine as a main regulator (along with K+ and lactate) of skeletal muscle blood flow.

Since beta-2 increases blood flow through the skeletal muscle and also increases cAMP, given that adenosine always decreases cAMP means that adenosine must cause vasoconstriction at the skeletal muscle.

I'd hope I'm getting my facts straight before jumping to conclusions like this.

Anyone else's thoughts on any of this stuff?

Adenosine is a coronary vasodilator (which is why we use it in cardiac stress testing) and a bronchoconstrictor (action opposed by theophylline). I'm not so sure about this vasoconstricting ability, but I do know that its coronary vasodilating activity, while sounding awesome, can actually cause coronary steal ischemia. As far as I can tell this is all you really need to know for Step 1. Could be wrong though.

 

[Phloston]

Adenosine is a coronary vasodilator (which is why we use it in cardiac stress testing) and a bronchoconstrictor (action opposed by theophylline). I'm not so sure about this vasoconstricting ability, but I do know that its coronary vasodilating activity, while sounding awesome, can actually cause coronary steal ischemia. As far as I can tell this is all you really need to know for Step 1. Could be wrong though.

Great input once again. You're 2 for 2 today, Aclamity. The RV hypertrophy thread was your other homerun.