scholarly journals EFFECTS OF GLUCAGON, PROSTAGLANDIN E1 AND DIBUTYRYL CYCLIC 3', 5'-AMP UPON THE TRANSMEMBRANE ACTION POTENTIAL OF GUINEA PIG VENTRICULAR FIBER AND MYOCARDIAL CONTRACTILE FORCE

1971 ◽  
Vol 35 (7) ◽  
pp. 807-819 ◽  
Author(s):  
TOSHIJI KOBAYASHI ◽  
RYU NAKAYAMA ◽  
KIYOJI KIMURA
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Prostaglandin E1 ◽  
Contractile Force ◽  
Transmembrane Action Potential ◽  
Myocardial Contractile Force ◽  
Myocardial Contractile

scholarly journals Influence of Glucose on the Transmembrane Action Potential of Papillary Muscle

1969 ◽  
Vol 53 (6) ◽  
pp. 792-815 ◽  
Author(s):  
Don P. MacLeod ◽  
K. Prasad
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Papillary Muscle ◽  
Glucose Concentration ◽  
Anaerobic Metabolism ◽  
Contractile Force ◽  
Control Value ◽  
Transmembrane Action Potential ◽  
Exogenous Glucose ◽  
Effect Of Glucose

The action potential duration (APD) of isolated guinea pig papillary muscle is directly related to the medium glucose concentration regardless of the gas mixture with which it is in equilibrium. The APD can be maintained at control value for many hours by a glucose concentration of 50 mM in the complete absence of oxygen. Following reduction of the APD by incubation of the muscle in medium containing 5 mM glucose, adjustment of the glucose concentration to 50 mM will cause restoration of normal APD. Phlorizin has been shown to competitively interfere with the effect of glucose on the APD and insulin to prevent or reverse the effect of phlorizin. Nonmetabolizable sugars cannot produce glucose-like effects on the APD. Adrenaline, noradrenaline, and isopropylnoradrenaline increased the reduced APD of papillary muscles incubated in the absence of oxygen in a medium containing 5 mM glucose coincident with an increase in contractile force. The effect of isopropylnoradrenaline was blocked by acetylcholine and propranolol. In the presence of iodoacetate and 2-deoxyglucose, isopropylnoradrenaline increased contractile force but not the reduced APD. Aminophylline was found to produce changes in the reduced APD similar to those caused by the sympathomimetic amines. The findings clearly support the hypothesis that anaerobic metabolism utilizing either glycogen or exogenous glucose is capable of maintaining normal transmembrane electrical activity in guinea pig papillary muscle.

Correlation between myocardial contractile force and cytosolic inorganic phosphate during early ischemia

1997 ◽  
Vol 272 (3) ◽  
pp. H1333-H1341 ◽  
Author(s):  
M. X. He ◽  
S. Wang ◽  
H. F. Downey
Keyword(s):  
Inorganic Phosphate ◽  
Contractile Force ◽  
Left Ventricular ◽  
Resonance Spectroscopy ◽  
Rat Hearts ◽  
Initial Control ◽  
Myocardial Contractile Force ◽  
Myocardial Contractile ◽  
Developed Pressure

To test the role of inorganic phosphate (Pi) in downregulation of myocardial contractile force at the onset of ischemia, Pi of rat hearts was determined with 31P nuclear magnetic resonance spectroscopy. Forty cycles of brief hypoperfusion (30% of baseline flow for 33 s) were used to achieve a time resolution of 0.512 s for comparing dynamic changes in Pi and contractile force. Initial control values of left ventricular developed pressure (LVP), heart rate, and oxygen consumption were 136 +/- 11 mmHg, 236 +/- 4 beats/min, and 95 +/- 3 microl O2 x min(-1) x g(-1); these values were unchanged at the end of the experiment. During the first 10 s of hypoperfusion, Pi increased at a rate (percentage of the total observed change) faster than the decrease in LVP; Pi and LVP then changed at the same rate during the remainder of the hypoperfusion. ADP did not change in advance of LVP. Intracellular pH did not change. The results indicate that Pi plays an important role in initiating the downregulation of myocardial contractile force at the onset of ischemia. Perfusion pressure also declined faster than LVP at the onset of ischemia, indicating potential importance of vascular collapse in contractile downregulation during early ischemia.

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