Most agree that DMT is metabolized quickly. The brain is set up to take it in directly. This is why its so short acting. But why is it that DMT can be found in the blood stream? Wouldnt the brain take the true domestically produced DMT in as soon as it was passed over the barrier? And if our brain "hungers" for it as suggested by some, how fast is it being metabolized compared to how fast its being created? I dont understand how there could be any surplus if its true that our brain soaks it in like a sponge...

Well as far as i know dmt is produced by the lungs and heart, and so it would make sense that its present in the bloodstream

I didnt know the lungs produced it. But still the question remains, how long is the new dmt in circulation before being taken up by the brain and replaced by new? Ten seconds after you smoke it your brain takes it in like crazy. So if its always in your blood stream isnt it fair to assume that the production rate is equal to or greater that the rate at which its metabolized? Is the brain the only place its broken down once its in the blood?

Think homeostasis. A flood of exogenous DMT (producing concentrations much greater than would occur naturally) will be metabolized much faster than than basal levels. Concentration of substrate is an important part of chemical equilibria. It's a fair assumption that basal levels of metabolism are on the same order of magnitude as basal levels of synthesis... but we would expect peak metabolism to be at least an order of magnitude greater.

Can you please send a link where it's proven it's produced in the lungs and heart?

I am really interested about this matter and how it is produced.

Even though there will be trace amounts of DMT in the blood, I believe the higher concentrations are found in the cerebro-spinal fluid (and I don't think those concentrations are really that high anyway). Even if endogenous DMT in the blood did make it to the brain without being broken down first, it would probably be such a small amount that you wouldn't notice anyway. When we smoke DMT, it's taking a very concentrated amount of DMT which can temporarily overload the system. Anyone with (or who has had) poor vaporization/smoking technique can attest to the fact that just because you manage to get DMT in your system, doesn't mean something spectacular or even really noticeable will happen. DMT in the blood just isn't concentrated enough to take effect. Perhaps in some natural altered states, it is because DMT has managed to achieve a substantial concentration to temporarily take effect.