Subcellular fractions of cyclic AMP and cyclic AMP-dependent protein kinase and the positive inotropic effects of selective beta 1- and beta 2-adrenoceptor agonists in guinea pig hearts.
We studied the effects of a full beta 1-adrenoceptor agonist (T-0509), a beta 2-adrenoceptor agonist (procaterol) and a nonselective beta-adrenoceptor agonist (isoproterenol, ISO) on subcellular cyclic AMP levels and cyclic AMP-dependent protein kinase (cyclic AMP-PK) activity in guinea pig hearts and compared them with the effect of each drug on cardiac contractility. T-0509 (10(-8)M) and ISO (3 x 10(-8)M) caused an increase of approximately 170% in dF/dtmax, whereas 10(-7) procaterol produced only a 25% increase. All these agonists significantly increased the cyclic AMP level in ventricular homogenate. Subcellular fractions were obtained by centrifugation at 100,000 g for 10 min and by Li2SO4 precipitation of the 100,000-g supernatant. In the control heart, probably salcolemmal protein, phospholamban, and 60-kDa protein in the particulate fraction and probably troponin I and troponin C in the supernatant fraction were mainly phosphorylated by the catalytic subunit of cyclic AMP-PK. In the precipitate obtained from the supernatant fraction with Li2SO4, probably all proteins described were contained. However, none of the proteins were detected in the supernatant obtained with Li2SO4. T-0509 and ISO caused significant changes in cyclic AMP levels and cyclic-PK activities in all fractions. However, procaterol increased the cyclic AMP concentrations and cyclic AMP-PK activities only in the supernatant fraction and the supernatant obtained with Li2SO4. T-0509 and ISO increased cyclic AMP level (9-16 pmol/mg protein) and cyclic AMP-PK activity ratio (0.27-0.33) significantly to the same degree in the precipitate obtained with Li2SO4, whereas the effects of T-0509 in other fractions were about twofold less than those of ISO. These results suggest that beta 1- and beta 2-adrenoceptor agonists cause differential compartmentalization of cyclic AMP and cyclic AMP-PK in the cardiac muscle.
Yabana
H
H
Lead Optimization Research Laboratory, Saitama, Japan.
Sasaki
Y
Y
Narita
H
H
Nagao
T
T
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D058665:Adrenergic beta-1 Receptor Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000032:analysis*; D006152:Cyclic GMP / Q000032:analysis*; D004983:Ethanolamines / Q000494:pharmacology; D006168:Guinea Pigs; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000737:chemistry* / Q000201:enzymology; D010766:Phosphorylation; D017265:Procaterol / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D013268:Stimulation, Chemical
D000316:Adrenergic alpha-Agonists; D058665:Adrenergic beta-1 Receptor Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D004983:Ethanolamines; D011506:Proteins; C025342:RP333; D017868:Cyclic AMP-Dependent Protein Kinases; D006152:Cyclic GMP; D017265:Procaterol