Pertussis toxin reduces the antiadrenergic effect of 2-chloroadenosine on papillary muscle and the direct negative inotropic effect of 2-chloroadenosine on atrium.
2-Chloroadenosine reduced the contractile tension of guinea-pig atria directly, and inhibited the increase in tension produced by beta-adrenergic stimulation of guinea-pig papillary muscle. Both effects were reduced by 8-phenyltheophylline, a competitive antagonist at extracellular P1-purinoceptors. Treatment of guinea-pigs with pertussis toxin reduced the sensitivity of both atria and ventricles to 2-chloroadenosine. Atria were significantly affected after treatment with 125 micrograms/kg toxin, but not 100 micrograms/kg. 60 micrograms/kg toxin had no effect on the sensitivity of the ventricles, but 100 and 125 micrograms/kg significantly decreased the antiadrenergic effect of 2-chloroadenosine. We conclude that both the direct and antiadrenergic effects are mediated by an inhibitory guanine nucleotide binding protein.
Hopwood
A M
AM
Cardiothoracic Institute, University of London, U.K.
Harding
S E
SE
Harris
P
P
D015762:2-Chloroadenosine; D000241:Adenosine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors; D000818:Animals; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009125:Muscle Relaxants, Central / Q000037:antagonists & inhibitors*; D009200:Myocardial Contraction / Q000187:drug effects*; D010210:Papillary Muscles / Q000187:drug effects; D037342:Pertussis Toxin; D013565:Sympatholytics / Q000037:antagonists & inhibitors*; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D009125:Muscle Relaxants, Central; D013565:Sympatholytics; D010566:Virulence Factors, Bordetella; D015762:2-Chloroadenosine; D013806:Theophylline; C028322:8-phenyltheophylline; D037342:Pertussis Toxin; D000241:Adenosine; D007545:Isoproterenol