Editing Dimethyltryptamine (section)

===Detection in body fluids===
DMT may be measured in blood, plasma or urine using chromatographic techniques as a diagnostic tool in clinical poisoning situations or to aid in the medicolegal investigation of suspicious deaths. In general, blood or plasma DMT levels in recreational users of the drug are in the 10–30 μg/L range during the first several hours post-ingestion.{{Citation needed|reason=Such precise values range needs one or more reliable sources|date=January 2012}} Less than 0.1% of an oral dose is eliminated unchanged in the 24-hour urine of humans.<ref>{{cite journal | vauthors = Callaway JC, Raymon LP, Hearn WL, McKenna DJ, Grob CS, Brito GS, Mash DC | title = Quantitation of ''N'',''N''-dimethyltryptamine and harmala alkaloids in human plasma after oral dosing with ayahuasca | journal = Journal of Analytical Toxicology | volume = 20 | issue = 6 | pages = 492–497 | date = October 1996 | pmid = 8889686 | doi = 10.1093/jat/20.6.492 | doi-access = free }}</ref><ref>{{cite book | vauthors = Baselt R | title = Disposition of Toxic Drugs and Chemicals in Man | edition = 9th | publisher = Biomedical Publications | location = Seal Beach, CA | date = 2011 | pages = 525–526 | isbn = 978-0-9626523-8-7 }}</ref>{{Clarify|date=March 2014|reason=unclear language, eliminated unchanged?}}

====Indolethylamine ''N''-methyltransferase (INMT)====
Before techniques of [[molecular biology]] were used to localize [[indolethylamine N-methyltransferase|indolethylamine ''N''-methyltransferase]] (INMT),<ref name="pmid9852119" /><ref name="pmid10552930" /> characterization and localization went on a par: samples of the biological material where INMT is hypothesized to be active are subject to [[enzyme assay]]. Those enzyme assays are performed either with a radiolabeled methyl donor like (<sup>14</sup>C-CH<sub>3</sub>)SAM to which known amounts of unlabeled substrates like tryptamine are added<ref name="pmid779022" /> or with addition of a radiolabeled substrate like (<sup>14</sup>C)NMT to demonstrate [[in vivo]] formation.<ref name="pmid6792104" /><ref name="pmid14361" /> As qualitative determination of the radioactively tagged product of the enzymatic reaction is sufficient to characterize INMT existence and activity (or lack of), analytical methods used in INMT assays are not required to be as sensitive as those needed to directly detect and quantify the minute amounts of endogenously formed DMT. The essentially qualitative method [[thin layer chromatography]] (TLC) was thus used in a vast majority of studies.<ref name="pmid779022" /> Also, robust evidence that INMT can catalyze transmethylation of tryptamine into NMT and DMT could be provided with [[Isotopic dilution|reverse isotope dilution analysis]] coupled to [[mass spectrometry]] for rabbit<ref name="pmid5150167">{{cite journal | vauthors = Mandel LR, Rosenzweig S, Kuehl FA | title = Purification and substrate specificity of indoleamine-''N''-methyl transferase | journal = Biochemical Pharmacology | volume = 20 | issue = 3 | pages = 712–716 | date = March 1971 | pmid = 5150167 | doi = 10.1016/0006-2952(71)90158-4 }}</ref><ref name="pmid1056183">{{cite journal | vauthors = Lin R, Narasimhachari N | title = ''N''-Methylation of 1-methyltryptamines by indolethylamine ''N''-methyltransferase | journal = Biochemical Pharmacology | volume = 24 | issue = 11–12 | pages = 1239–1240 | date = June 1975 | pmid = 1056183 | doi = 10.1016/0006-2952(75)90071-4 }}</ref> and human<ref name="pmid5034200">{{cite journal | vauthors = Mandel LR, Ahn HS, VandenHeuvel WJ | title = Indoleamine-''N''-methyl transferase in human lung | journal = Biochemical Pharmacology | volume = 21 | issue = 8 | pages = 1197–1200 | date = April 1972 | pmid = 5034200 | doi = 10.1016/0006-2952(72)90113-X }}</ref> lung during the early 1970s.

Selectivity rather than sensitivity proved to be a challenge for some TLC methods with the discovery in 1974–1975 that incubating rat blood cells or brain tissue with (<sup>14</sup>C-CH<sub>3</sub>)SAM and NMT as substrate mostly yields tetrahydro-β-carboline derivatives,<ref name="pmid779022" /><ref name="pmid6792104" /><ref name="pmid1067427">{{cite journal | vauthors = Rosengarten H, Meller E, Freidhoff AJ | title = Possible source of error in studies of enzymatic formation of dimethyltryptamine | journal = Journal of Psychiatric Research | volume = 13 | issue = 1 | pages = 23–30 | year = 1976 | pmid = 1067427 | doi = 10.1016/0022-3956(76)90006-6 }}</ref> and negligible amounts of DMT in brain tissue.<ref name="pmid779022" /> It is indeed simultaneously realized that the TLC methods used thus far in almost all published studies on INMT and DMT biosynthesis are incapable to resolve DMT from those tetrahydro-β-carbolines.<ref name="pmid779022" /> These findings are a blow for all previous claims of evidence of INMT activity and DMT biosynthesis in avian<ref name="pmid5793241">{{cite journal | vauthors = Morgan M, Mandell AJ | title = Indole(ethyl)amine ''N''-methyltransferase in the brain | journal = Science | volume = 165 | issue = 3892 | pages = 492–493 | date = August 1969 | pmid = 5793241 | doi = 10.1126/science.165.3892.492 | bibcode = 1969Sci...165..492M | s2cid = 43317224 }}</ref> and mammalian brain,<ref name="pmid5279043">{{cite journal | vauthors = Mandell AJ, Morgan M | title = Indole(ethyl)amine ''N''-methyltransferase in human brain | journal = Nature | volume = 230 | issue = 11 | pages = 85–87 | date = March 1971 | pmid = 5279043 | doi = 10.1038/newbio230085a0 }}</ref><ref name="pmid4703789">{{cite journal | vauthors = Saavedra JM, Coyle JT, Axelrod J | title = The distribution and properties of the nonspecific ''N''-methyltransferase in brain | journal = Journal of Neurochemistry | volume = 20 | issue = 3 | pages = 743–752 | date = March 1973 | pmid = 4703789 | doi = 10.1111/j.1471-4159.1973.tb00035.x | s2cid = 42038762 }}</ref> including [[in vivo]],<ref name="pmid5059565">{{cite journal | vauthors = Saavedra JM, Axelrod J | title = Psychotomimetic ''N''-methylated tryptamines: formation in brain in vivo and in vitro | journal = Science | volume = 175 | issue = 4028 | pages = 1365–1366 | date = March 1972 | pmid = 5059565 | doi = 10.1126/science.175.4028.1365 | url = http://crfdl.org:1111/xmlui/bitstream/handle/123456789/392/1733285.pdf?sequence=1 | format = PDF | bibcode = 1972Sci...175.1365S | s2cid = 30864349 }}{{Dead link|date=July 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="pmid4725358">{{cite journal | vauthors = Wu PH, Boulton AA | title = Distribution and metabolism of tryptamine in rat brain | journal = Canadian Journal of Biochemistry | volume = 51 | issue = 7 | pages = 1104–1112 | date = July 1973 | pmid = 4725358 | doi = 10.1139/o73-144 }}</ref> as they all relied upon use of the problematic TLC methods:<ref name="pmid779022" /> their validity is doubted in replication studies that make use of improved TLC methods, and fail to evidence DMT-producing INMT activity in rat and human brain tissues.<ref name="pmid963555">{{cite journal | vauthors = Boarder MR, Rodnight R | title = Tryptamine-''N''-methyltransferase activity in brain tissue: a re-examination | journal = Brain Research | volume = 114 | issue = 2 | pages = 359–364 | date = September 1976 | pmid = 963555 | doi = 10.1016/0006-8993(76)90680-6 | s2cid = 36334101 }}</ref><ref name="pmid823298">{{cite journal | vauthors = Gomes UR, Neethling AC, Shanley BC | title = Enzymatic N-methylation of indoleamines by mammalian brain: fact or artefact? | journal = Journal of Neurochemistry | volume = 27 | issue = 3 | pages = 701–705 | date = September 1976 | pmid = 823298 | doi = 10.1111/j.1471-4159.1976.tb10397.x | s2cid = 6043841 }}</ref> Published in 1978, the last study attempting to evidence [[in vivo]] INMT activity and DMT production in brain (rat) with TLC methods finds biotransformation of radiolabeled tryptamine into DMT to be real but "insignificant".<ref name="pmid279646">{{cite journal | vauthors = Stramentinoli G, Baldessarini RJ | title = Lack of enhancement of dimethyltryptamine formation in rat brain and rabbit lung in vivo by methionine or ''S''-adenosylmethionine | journal = Journal of Neurochemistry | volume = 31 | issue = 4 | pages = 1015–1020 | date = October 1978 | pmid = 279646 | doi = 10.1111/j.1471-4159.1978.tb00141.x | s2cid = 26099031 }}</ref> Capability of the method used in this latter study to resolve DMT from tetrahydro-β-carbolines is questioned later.<ref name="pmid6792104"/>

To localize INMT, a qualitative leap is accomplished with use of modern techniques of [[molecular biology]], and of [[immunohistochemistry]]. In humans, a gene encoding INMT is determined to be located on [[Chromosome 7 (human)|chromosome 7]].<ref name="pmid10552930" /> [[Northern blot|Northern blot analyses]] reveal INMT [[messenger RNA]] (mRNA) to be highly expressed in rabbit lung,<ref name="pmid9852119" /> and in human [[thyroid]], [[adrenal gland]], and lung.<ref name="pmid10552930" /><ref name="UniProtO95050">{{cite web|url=https://www.uniprot.org/uniprot/O95050|title=INMT – Indolethylamine ''N''-methyltransferase – ''Homo sapiens'' (Human) – INMT gene & protein|website=Uniprot.org|access-date=2018-03-24|archive-date=2018-09-20|archive-url=https://web.archive.org/web/20180920111803/https://www.uniprot.org/uniprot/O95050|url-status=live}}</ref> Intermediate levels of expression are found in human heart, skeletal muscle, trachea, stomach, small intestine, pancreas, testis, prostate, placenta, [[lymph node]], and spinal cord.<ref name="pmid10552930" /><ref name="UniProtO95050" /> Low to very low levels of expression are noted in rabbit brain,<ref name="pmid10552930" /> and human [[thymus]], liver, [[spleen]], kidney, colon, ovary, and [[bone marrow]].<ref name="pmid10552930" /><ref name="UniProtO95050" /> INMT mRNA expression is absent in human peripheral blood [[White blood cell|leukocytes]], whole brain, and in tissue from seven specific brain regions (thalamus, subthalamic nucleus, caudate nucleus, hippocampus, amygdala, substantia nigra, and corpus callosum).<ref name="pmid10552930" /><ref name="UniProtO95050" /> [[Immunohistochemistry]] showed INMT to be present in large amounts in [[Goblet cell|glandular epithelial cells]] of small and large intestines. In 2011, immunohistochemistry revealed the presence of INMT in primate nervous tissue including retina, spinal cord motor neurons, and pineal gland.<ref name="Cozzi N.V., Mavlyutov T.A., Thompson M.A., Ruoho A.E. 2011 840.19">{{cite journal | vauthors = Cozzi NV, Mavlyutov TA, Thompson MA, Ruoho AE | title = Indolethylamine N-methyltransferase expression in primate nervous tissue. | journal = Society for Neuroscience Abstracts | date = 2011 | volume = 37 | pages = 840.19 |url=http://www.neurophys.wisc.edu/~cozzi/Indolethylamine%20N-methyltransferase%20expression%20in%20primate%20nervous%20tissue.pdf |access-date=20 September 2012|archive-url=https://web.archive.org/web/20120913184820/http://www.neurophys.wisc.edu/~cozzi/Indolethylamine%20N-methyltransferase%20expression%20in%20primate%20nervous%20tissue.pdf|archive-date=13 September 2012}}</ref> A 2020 study using [[in-situ hybridization]], a far more accurate tool than the northern blot analysis, found mRNA coding for INMT expressed in the human cerebral cortex, choroid plexus, and pineal gland.<ref name = "Dean_2019" />