Prostaglandin E2 synthesis elicited by adrenergic stimuli in guinea pig trachea is mediated primarily via activation of beta 2 adrenergic receptors.
Prostaglandin (PG) E2 synthesis elicited by adrenergic agonists in the guinea pig trachea has been shown to be mediated via activation of beta-adrenergic receptors. The purpose of this study was to examine arachidonic acid (AA) metabolism and to characterize the subtype of beta receptor involved in PG synthesis. [14C]AA was incubated with guinea pig tracheal rings, and the radiolabelled products were extracted from the medium. Thin layer chromatographic analysis and radioimmunoassay of the extract showed that [14C]AA was incorporated into guinea pig tracheal rings and metabolized mainly into radiolabeled and immunoreactive PGE2 (iPGE2) and smaller amounts into PGF2 alpha. Trace amounts of PGD2, TxB2 and 6-keto-PGF1 alpha but not LTB4 or LTC4 were detected by enzyme immunoassay. Incubation of guinea pig tracheal rings for 10 min with isoproterenol or salbutamol resulted in a significant increase in PGE2 synthesis (optimum concentration 0.1 microM for both compounds). In contrast, dobutamine, BRL 37344, BRL 28410, norepinephrine, phenylephrine, and xylazine (up to 1 microM) did not significantly increase PGE2 production. Isoproterenol-induced iPGE2 production was inhibited by the selective beta 2 receptor antagonist butoxamine (0.1-1.0 microM) and somewhat reduced by the beta 1 receptor antagonist practolol (1 microM). The increase in PGE2 synthesis was diminished with increasing concentrations of isoproterenol (0.5-5.0 microM) or salbutamol (0.5-1.0 microM); but it was reversed by pretreatment of tracheal rings with the protein synthesis inhibitors cycloheximide (0.9 microM) and actinomycin D (2 microM) but not by phenylisopropyl adenosine (0.1-1.0 microM), an inhibitor of adenylyl cyclase. These data suggest that isoproterenol-induced iPGE2 synthesis is primarily via activation of a beta 2 adrenergic receptor. Failure to enhance iPGE2 synthesis by a high concentration of isoproterenol is likely to be due to an induction of new inhibitory protein synthesis.
Lew
D B
DB
Department of Pediatrics, College of Medicine, University of Tennessee, Memphis 38163.
Nadel
G L
GL
Malik
K U
KU
D000420:Albuterol / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002078:Butoxamine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis*; D004280:Dobutamine / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D011217:Practolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013997:Time Factors; D014132:Trachea / Q000502:physiology*
D011943:Receptors, Adrenergic, beta; D002078:Butoxamine; D003609:Dactinomycin; D005576:Colforsin; D016718:Arachidonic Acid; D004280:Dobutamine; D003513:Cycloheximide; D000242:Cyclic AMP; D015232:Dinoprostone; D007545:Isoproterenol; D000420:Albuterol; D011217:Practolol