Tissue content of opioid peptides in the myenteric plexus-longitudinal muscle of guinea-pig small intestine.
We have developed a method that is based on two HPLC systems and permits the separation of endogenous opioid peptides in tissue extracts. The individual peptides are bioassayed on the mouse isolated vas deferens; naloxone (100 nM) ensures opioid specificity. In the myenteric plexus-longitudinal muscle preparation of the guinea-pig small intestine, the tissue content of prodynorphin-derived peptides is lower than those of proenkephalin-derived peptides. No beta-endorphin was detected. Of the prodynorphin fragments, alpha-neoendorphin, beta-neoendorphin, dynorphin A(1-8), and dynorphin B are present in equimolar concentrations (12-15 pmol/g) whereas the tissue content of dynorphin A is only 0.8 pmol/g. Processing of proenkephalin leads to at least six opioid peptides. The tissue contents of [Leu5]enkephalin, [Met5]enkephalyl-Arg-Gly-Leu, and [Met5]enkephalyl-Arg-Phe are 90-100 pmol/g and the content of [Met5]enkephalin is 405 pmol/g. BAM-18 and [Met5]enkephalyl-Arg-Arg-Val-NH2 are present in much lower concentrations, 24 and 5 pmol/g, respectively. Although present in low amounts, BAM-18 and [Met5]-enkephalyl-Arg-Arg-Val-NH2 have high affinity for the mu-opioid binding site and to a lesser extent for the kappa-site; this binding profile differs from that of the other proenkephalin fragments all of which have high affinities for the mu- and delta-sites.
Corbett
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Unit for Research on Addictive Drugs, University of Aberdeen, Marischal College, Scotland.
McKnight
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Kosterlitz
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D000818:Animals; D001681:Biological Assay; D002851:Chromatography, High Pressure Liquid; D004723:Endorphins / Q000032:analysis* / Q000494:pharmacology; D004743:Enkephalin, Leucine / Q000032:analysis; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives / Q000032:analysis; D004745:Enkephalins / Q000032:analysis; D006168:Guinea Pigs; D007421:Intestine, Small / Q000032:analysis* / Q000294:innervation; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009197:Myenteric Plexus / Q000032:analysis*; D009270:Naloxone / Q000494:pharmacology; D011498:Protein Precursors / Q000032:analysis; D014018:Tissue Distribution; D014649:Vas Deferens / Q000187:drug effects / Q000502:physiology
D004723:Endorphins; D004745:Enkephalins; D011498:Protein Precursors; D009270:Naloxone; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; C033660:preproenkephalin