Beta-adrenergic relaxation of dog trachealis: contractile agonist-specific interaction.
The phenomenon of contractile agonist-dependent relaxation by isoproterenol (ISO) of active tension elicited by acetylcholine (ACh), histamine (HIS), serotonin (5-HT), and potassium chloride-substituted Krebs-Henseleit solution (KCl) was studied in 210 tracheal smooth muscle (TSM) strips from 28 mongrel dogs in vitro. All TSM strips were contracted to similar active tensions [target tension (TT) = 50% of the maximal active tension elicited by 127 mM KCl] with ACh, HIS, 5-HT, or KCl and relaxed with either ISO, forskolin (FSK), N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate (db-cAMP), or 3-isobutyl-1-methylxanthine (IMX). The concentrations of ISO causing 50% relaxation from TT (RC50) were ACh (2.9 +/- 1.1 x 10(-6) M) greater than 5-HT (8.4 +/- 1.5 x 10(-8) M) approximately KCl (8.1 +/- 2.1 x 10(-8) M) greater than HIS (1.6 +/- 0.2 x 10(-8) M). FSK and IMX relaxed TSM in the same rank order of potency as ISO. In contrast to the contractile agonist-dependent relaxation elicited by ISO, FSK, and IMX, db-cAMP was nearly equipotent in relaxing similarly contracted strips. These results are consistent with contractile agonist-specific interaction with cAMP production by ISO and FSK. These data demonstrate that the phenomenon of contractile agonist-dependent relaxation by ISO is not related specifically to the beta-adrenoceptor.
Koenig
S M
SM
Division of Biological Sciences, University of Chicago, Illinois 60637.
Mitchell
R W
RW
Kelly
E
E
White
S R
SR
Leff
A R
AR
Popovich
K J
KJ
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004285:Dogs; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D011189:Potassium Chloride / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology*; D014132:Trachea / Q000187:drug effects* / Q000502:physiology
D000318:Adrenergic beta-Agonists; D005576:Colforsin; D012701:Serotonin; D003994:Bucladesine; D011189:Potassium Chloride; D006632:Histamine; D007545:Isoproterenol; D000109:Acetylcholine; D015056:1-Methyl-3-isobutylxanthine