Myocardial adenosine A1 and A2 receptor activities during juvenile and adult stages of development

摘要: Myocardial contractile responsiveness to beta-adrenoceptor stimulation is known be reduced with maturation or aging. The present study was undertaken determine the role of antiadrenergic A1 and stimulatory A2 adenosine receptors in modulation beta-adrenergic-elicited performance heart at juvenile (approximately 25 days) adult 79 stages maturation. Isoproterenol, a beta-adrenergic agonist, 10(-7) M produced greater maximal increase contractility, assessed as rate left ventricular pressure development (+dP/dtmax), immature than mature hearts (104 80%, respectively), but venous concentration (738 277 nM, respectively). Isoproterenol 10(-9) 10(-8) similar increases contractility absence presence receptor antagonist xanthine amine congener (XAC; 0.5 microM) for both hearts. In addition, XAC did not alter isoproterenol-elicited response during hypoperfusion induced by 50% reduction coronary flow. However, heart, isoproterenol elicited significantly +dP/dtmax (79%) vs. (60%) XAC. hearts, enhanced magnitudes 76 72%, respectively. further studies, 9-chloro-2-(2-furyl)[1,2,4]-triazolo[1,5-c]quinazolin-5-amine (CGS-15943; 1 normal perfusion. These results suggest that myocardial modulates via activation these functions become expressed