title: Neurohormonal regulation of ion transport in the porcine distal jejunum. Enhancement of sodium and chloride absorption by submucosal opiate receptors.
abstract: The actions of opiates in modulating ion transport across the porcine distal jejunal mucosa were examined in vitro. Opiate receptors were functionally characterized using [D-Pen2,D-Pen5]-enkephalin (DPDPE), [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) and U-50,488 (trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)- cyclohexyl]-benzeneacetamide), agonists selective for delta, mu and kappa receptor types, respectively. Serosal administration of opiate agonists produced concentration-dependent decreases in basal short-circuit current (Isc. DPDPE and DAMGO also increased tissue conductance (Gt). DPDPE (EC50 = 4 nM) was 7- and 86-fold more potent in decreasing basal Isc than DAMGO and U-50,488, respectively. U-50,488 displayed the greatest efficacy in decreasing Isc. Serosal naloxone decreased DPDPE and DAMGO potencies under basal conditions with Ke values of 11 and 6 nM, respectively. DPDPE- and DAMGO-induced decreases in basal Isc were associated with increases in net Cl absorption; in addition, DAMGO produced an increase in net Na absorption. 8-Bromocyclic AMP (0.3 mM) increased Isc, decreased Gt and inhibited net Na and Cl absorptive fluxes. Selective opiate agonists decreased cyclic AMP-induced elevations in Isc with a rank order of potency (DPDPE, EC50 = 3 nM) of DPDPE greater than DAMGO greater than U-50,488. DPDPE reversed the action of cyclic AMP on Isc and Cl absorption but had no effect on net Na transport. Cyclic AMP-induced decreases in Gt were not altered by DPDPE.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Veterinary Biology (Pharmacology Section), College of Veterinary Medicine, University of Minnesota, St. Paul.
authors.forename: F L
authors.initials: FL
authors.lastname: Quito
authors.forename: D R
authors.initials: DR
authors.lastname: Brown
mesh_terms: D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D002712:Chlorides / Q000378:metabolism*; D004558:Electric Stimulation; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects; D007583:Jejunum / Q000187:drug effects* / Q000378:metabolism; D009294:Narcotics / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000187:drug effects* / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects*; D013552:Swine
chemical_list: D000700:Analgesics; D002712:Chlorides; D004745:Enkephalins; D007473:Ion Channels; D009294:Narcotics; D011957:Receptors, Opioid; D015222:Sodium Channels; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D020881:Enkephalin, D-Penicillamine (2,5)-