The Effect of Noradrenaline and Tyramine on Cardiac Contractility, Cyclic AMP, and Phosphorylase a in Normal and Hyperthyroid Rats

1974 ◽  
Vol 52 (3) ◽  
pp. 375-383 ◽  
Author(s):  
Beverley A. Young ◽  
John H. McNeill
Keyword(s):  
Cyclic Amp ◽  
Rat Heart ◽  
Cardiac Contractility ◽  
Time Response ◽  
Dependent Manner ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart ◽  
Hyperthyroid State ◽  
Dose Dependent ◽  
Higher Doses

Noradrenaline and tyramine increased contractility, phosphorylase a, and cyclic AMP in a dose-dependent manner in the isolated perfused rat heart. Time–response studies revealed that cyclic AMP was increased by both amines before the increase in contractility. Hearts from hyperthyroid rats responded to noradrenaline in a manner similar to control hearts when contractility or cyclic AMP was measured. The phosphorylase activating effect of noradrenaline was enhanced in the hyperthyroid hearts. It was concluded that a non-cyclic AMP mechanism was involved in the enhancement. The effects of tyramine on contractility and cyclic AMP were decreased in the hearts from hyperthyroid animals when compared with control hearts. Phosphorylase activation by tyramine was not enhanced by the hyperthyroid state and was in fact reduced at higher doses of tyramine.

scholarly journals The release of 3′:5′-cyclic monophosphate from the isolated perfused rat heart

1975 ◽  
Vol 152 (2) ◽  
pp. 429-432 ◽  
Author(s):  
John A. O'Brien ◽  
Richard C. Strange
Keyword(s):  
Cyclic Amp ◽  
Rat Heart ◽  
Perfused Rat Heart ◽  
Cyclic Monophosphate ◽  
Isolated Perfused Rat Heart ◽  
Rat Hearts ◽  
Basal Release ◽  
Perfused Rat Hearts ◽  
Isolated Perfused Rat Hearts

Although basal release of cyclic AMP from isolated perfused rat hearts was not measurable, isoprenaline induced substantial release of the nucleotide, suggesting that in vivo the myocardium can contribute to plasma cyclic AMP. Anoxia also increased the amount of cyclic AMP released, but insulin and nicotinate alone or in combination had no effect.

scholarly journals Zidovudine Inhibits Thymidine Phosphorylation in the Isolated Perfused Rat Heart

2007 ◽  
Vol 51 (4) ◽  
pp. 1142-1149 ◽  
Author(s):  
Delia Susan-Resiga ◽  
Alice T. Bentley ◽  
Matthew D. Lynx ◽  
Darcy D. LaClair ◽  
Edward E. McKee
Keyword(s):  
Mitochondrial Dna ◽  
Dna Replication ◽  
Thymidine Kinase ◽  
Rat Heart ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart ◽  
Mitochondrial Dna Depletion ◽  
Mitochondrial Dna Replication

ABSTRACT Zidovudine (AZT; 3′-azido-3′-deoxythymidine), a thymidine analog, has been a staple of highly active antiretroviral therapy. It is phosphorylated in the host to the triphosphate and functions by inhibiting the viral reverse transcriptase. However, long-term use of AZT is linked to various tissue toxicities, including cardiomyopathy. These toxicities are associated with mitochondrial DNA depletion, which is hypothesized to be caused by AZT triphosphate inhibition of mitochondrial DNA polymerase γ. In previous work with isolated heart mitochondria, we demonstrated that AZT phosphorylation beyond the monophosphate was not detected and that AZT itself was a potent inhibitor of thymidine phosphorylation. This suggests an alternative hypothesis in which depletion of the TTP pool may limit mitochondrial DNA replication. The present work extends these studies to the whole cell by investigating the metabolism of thymidine and AZT in the intact isolated perfused rat heart. [3H]thymidine is converted to [3H]TTP in a time- and concentration-dependent manner. The level of [3H]TMP is low, suggesting that the reaction catalyzed by thymidine kinase is the rate-limiting step in phosphorylation. [3H]AZT is converted in a time- and concentration-dependent manner to AZT monophosphate, the only phosphorylated product detected after 3 h of perfusion. Both compounds display negative cooperativity, similar to the observations with cloned and purified mitochondrial thymidine kinase 2. The presence of AZT in the perfusate inhibits the phosphorylation of [3H]thymidine with a 50% inhibitory concentration of 24 ± 4 μM. These data support the hypothesis that AZT-induced mitochondrial cardiotoxicity may be caused by a limiting pool of TTP that lowers mitochondrial DNA replication.

Location of epicardial pacemaker electrodes and myocardial contractility

1969 ◽  
Vol 47 (3) ◽  
pp. 267-271 ◽  
Author(s):  
G. M. Tremblay ◽  
M. Nahas
Keyword(s):  
Rat Heart ◽  
Myocardial Contractility ◽  
Calcium Concentration ◽  
Cardiac Contractility ◽  
Sprague Dawley ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart ◽  
Sprague Dawley Rats ◽  
Significant Difference ◽  
Pacemaker Electrodes

Effects of pacing from different epicardial sites on cardiac contractility were studied in the isolated perfused rat heart. An indwelling balloon containing a known volume of saline was used to record intracavitary pressure (LVP), force, and maximum dp/dt during isovolumic paced contraction. Coronary flow was kept constant, and the adequacy of oxygenation was verified by lactate extraction. Forty male Sprague–Dawley rats weighing 250–300 g were divided into two groups, according to the rate of pacing, and stimulated. Pacing from four different epicardial sites failed to show any statistically significant difference in LVP, force, or maximum dp/dt at either different heart rate or calcium concentration. The present study suggests that myocardial contractility in the isolated perfused rat heart is not affected by the pacing site of the epicardial pacemaker.

Global ischemic duration and reperfusion function in the isolated perfused rat heart

Resuscitation ◽  
2004 ◽  
Vol 62 (1) ◽  
pp. 97-106 ◽  
Author(s):  
Brian S. Palmer ◽  
Mersiha Hadziahmetovic ◽  
Timothy Veci ◽  
Mark G. Angelos
Keyword(s):  
Rat Heart ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart ◽  
Ischemic Duration
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