Regulation of L-valine absorption by opioids interacting with mu-receptors in rabbit ileum.
In intact tissue, [D-Ala2,MePhe4,Gly-ol5]enkephalin (10(-5) M; mu-ligand), diminished short-circuit current (Isc) and increased water, Na+ and Cl- net fluxes in vitro under open circuit conditions; it also inhibited L-valine absorption and L-valine-dependent variations of short-circuit current (delta Isc,val). Naloxone (10(-6) M) antagonized these effects. In the absence of the muscularis and myenteric plexus this enkephalin or morphine (mu-ligand) reduced Isc and delta Isc,val. These enkephalin effects occurred at different times. Different concentrations of enkephalin were tested for their effects on delta Isc,val. [D-Ala2,D-Leu5]enkephalin (mainly a delta-ligand) significantly decreased Isc but not delta Isc,val. The reduction of L-valine absorption does not depend on the effects on basal ion transport. Interaction of opioids with mu-receptors located in the submucosal plexus and/or in the epithelial cell accounts for this reduction. This enkephalin effect seems to be at least partially under the control of the myenteric plexus.
D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001834:Body Water / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D016308:Enkephalin, Leucine-2-Alanine / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology*; D007082:Ileum / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009020:Morphine / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009270:Naloxone / Q000494:pharmacology; D011817:Rabbits; D017450:Receptors, Opioid, mu / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D013997:Time Factors; D014633:Valine / Q000378:metabolism*
D000700:Analgesics; D002712:Chlorides; D004745:Enkephalins; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009270:Naloxone; D016308:Enkephalin, Leucine-2-Alanine; D009020:Morphine; D012964:Sodium; D014633:Valine