title: Two relaxation-mediating P2-purinoceptors in guinea-pig taenia caeci.
abstract: 2-Methylthio ATP, noradrenaline, adenosine 5'-O-(2-thiodiphosphate) (ADP beta S), alpha, beta-methylene ATP, ATP and adenosine caused relaxation of guinea-pig isolated taenia caeci precontracted by carbachol, with potency decreasing in the order indicated. 4,4'-Diisothiocyanatostilbene-2,2'-disulphonate (DIDS) 10, 32 and 100 microM shifted the concentration-response curve of alpha, beta-methylene ATP increasingly to the right, by the factor 141 at DIDS 100 microM. Concentration-response curves of the other agonists were not shifted to the right by DIDS 100 microM, except for the curve of ADP beta S which was shifted by the factor 2.4. The relaxation produced by 2-methylthio ATP faded rapidly. When the fade was complete, further addition of 2-methylthio ATP or ATP did not elicit relaxation, whereas the relaxant effect of alpha, beta-methylene ATP was unchanged. The results indicate that there are at least two relaxation-mediating P2-purinoceptors in guinea-pig taenia caeci, the P2Y-purinoceptor which is relatively insensitive to DIDS and a distinct receptor for alpha, beta-methylene ATP which is very sensitive to DIDS.
authors.affiliation: Pharmakologisches Institut, Universität Freiburg, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Dudeck
authors.forename: R
authors.initials: R
authors.lastname: Bültmann
authors.forename: K
authors.initials: K
authors.lastname: Starke
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000818:Animals; D002432:Cecum / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000502:physiology*
chemical_list: D018048:Receptors, Purinergic P2; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid