James G. Dobson

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The properties of adenosine inhibition of catecholamine-induced responses were investigated, using an isolated rat heart preparation. Perfusion of hearts with 0.1 microM isoproterenol increased myocardial cAMP content 2.8-fold, activation of cAMP-dependent protein kinase 4.4-fold, phosphorylase a formation 3.4-fold, left ventricular pressure 1.8-fold, rate(More)
Experiments were performed on isolated frog sartorius muscle and in situ dog skeletal muscle to determine whether adenine nucleotides and their degradation products are released during contraction in concentrations capable of producing arteriolar dilation. ATP was not detectable ( < 1 O 8 M ) in the bathing solution of the resting or contracting frog(More)
Adenosinergic and muscarinic agents have been shown to attenuate the catecholamine-induced augmentation of both protein phosphorylation and contractile state in perfused hearts. The attenuation by phenylisopropyl-adenosine (PIA) and carbamylcholine chloride (CARB) of the isoproterenol (ISO)-induced incorporation of 32P into protein substrates was examined(More)
Adenosine levels present in the interstitial fluid and coronary effluent of the aged heart exceed those of the young adult heart. The present study investigated mechanisms in the Fischer 344 rat heart which may be responsible for the observed differences. (1) Total production of adenosine was determined in isolated perfused hearts by measuring coronary(More)
BACKGROUND Increased sympathetic activity contributes to the progression of heart failure. Adenosine counteracts sympathetic activity by inhibition of presynaptic norepinephrine release and attenuation of the metabolic and contractile responses to beta-adrenergic stimulation. In this study, we tested the hypothesis that the adenosinergic effects (uptake(More)
Multiple brief periods of ischemia in the mammalian heart elicits protection against morphologic and functional damage caused by longer-duration ischemia. Preconditioning-induced protection against post-ischemic contractile dysfunction has been reported to be depressed with aging of the adult heart. This study was undertaken to determine whether aging of(More)
Adenosine A(2a)-receptor activation enhances shortening of isolated cardiomyocytes. In the present study the effect of A(2a)-receptor activation on the contractile performance of isolated rat hearts was investigated by recording left ventricular pressure (LVP) and the maximal rate of LVP development (+dP/dt(max)). With constant-pressure perfusion, adenosine(More)
The relationship between changes in the myocardial concentration of adenosine 3':5'-cyclic monophosphate (cyclic AMP) and cardiac contractility was studied in guinea pig and rat myocardium. When isolated perfused guinea pig heart were perfused with 10-5-M papaverine, a potent inhibitor of cyclic AMP phosphodiesterase activity, myocardial cyclic AMP(More)