Pertussis toxin pretreatment alters agonist binding to beta-adrenoceptors in rabbit ventricular myocardium.
The influence of pretreatment with pertussis toxin (PTX) on characteristics of beta-adrenoceptor bindings was examined in myocardial ventricular membranes prepared from rabbits which received an intravenous injection of PTX (10 micrograms/kg) or its vehicle. The density and affinity of beta-adrenoceptors assessed by (-)-[125I]iodocyanopindolol were not significantly altered by PTX pretreatment. However, a fraction of agonist binding sites with high affinity significantly increased in PTX-pretreated myocardial membranes. In the presence of 100 microM 5'-guanylyl imidodiphosphate, all agonist binding sites were converted to low-affinity sites in both control and PTX-pretreated membranes. The results suggest that Gi might regulate negatively coupling of beta-adrenoceptors to Gs.
Akaishi
Y
Y
Department of Pharmacology, Hokkaido University School of Medicine, Sapporo, Japan.
Hattori
Y
Y
Kanno
M
M
Sakuma
I
I
Kitabatake
A
A
D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006352:Heart Ventricles / Q000378:metabolism; D007457:Iodine Radioisotopes; D020120:Iodocyanopindolol; D007545:Isoproterenol; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D037342:Pertussis Toxin; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D007457:Iodine Radioisotopes; D011943:Receptors, Adrenergic, beta; D010566:Virulence Factors, Bordetella; D006165:Guanylyl Imidodiphosphate; D020120:Iodocyanopindolol; D010869:Pindolol; D037342:Pertussis Toxin; D007545:Isoproterenol