THE ACTION POTENTIAL OF THE MYOCARDIAL CELLS OF THE GOLDEN CARP

The negative inotropic effect of a commonly used formulation of bradykinin (Sandoz BRS-640) was found to be due to chlorobutanol, a constituent of the preparation. Solutions containing up to 100 mug of crystalline bradykinin/ml had no effect on tension or action-potential shape. Chlorobutanol (500 mug/ml) caused a 30% decrease in contraction amplitude and a 20% increase in action-potential duration. Chlorobutanol lowered conduction velocity and induced conduction failure and automaticity within isolated ventricular muscle strips. Chlorobutanol affected neither positive nor negative treppe. We conclude that bradykinin has no direct action on toad, frog, or rat myocardium. However, chlorobutanol does have direct effects on myocardial cells, acting on the cell membrane and decreasing isometric tension produced by the heart.

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The Effect of Cytotoxic Lymphocytes on Contraction, Action Potential and Calcium Handling in Cultured Myocardial Cells

Advances in Experimental Medicine and Biology - Molecular and Subcellular Cardiology ◽

10.1007/978-1-4615-1893-8_23 ◽

1995 ◽

pp. 229-238 ◽

Cited By ~ 1

Author(s):

Yonathan Hasin ◽

Yael Eilam ◽

David Hassin ◽

Ruhama Fixler

Keyword(s):

Action Potential ◽

Calcium Handling ◽

Cytotoxic Lymphocytes ◽

Myocardial Cells ◽

Cultured Myocardial Cells

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Electrophysiological properties of cultured adult rat ventricular cardiac muscle cells

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1986.250.5.h731 ◽

1986 ◽

Vol 250 (5) ◽

pp. H731-H735

Author(s):

C. F. Meier ◽

G. M. Briggs ◽

W. C. Claycomb

Keyword(s):

Action Potential ◽

Cultured Cells ◽

Resting Potential ◽

Myocardial Tissue ◽

Myocardial Cells ◽

Isolated Cells ◽

Cardiac Muscle Cells ◽

Electrophysiological Properties ◽

Adult Rat ◽

Average Maximum

Action and resting potential characteristics of isolated adult rat myocardial cells maintained in culture for 10–28 days are described. Resting potentials averaged -76.3 +/- 2 mV in 5 mM extracellular [K+] ([K+]o). Resting potentials changed by 54.3 mV/decade change in [K+]o for concentrations greater than 5 mM. The average maximum rate of rise of action potential (Vmax) was 117.7 +/- 10 V/s with overshoots of 34.6 +/- 2.5 mV. Action potential durations (APD) to 0 and -40 mV and full repolarization were 21.8 +/- 3.9, 36.3 +/- 6.0, and 206 +/- 16.9 ms respectively. Action potential configurations were qualitatively similar to those previously reported by others for rat myocardial tissue or freshly dissociated cells. Tetrodotoxin (4 micrograms/ml) decreased Vmax to less than 24 V/s and decreased overshoot and APD. Isoproterenol (10(-8) M) decreased APD with slight elevation of the overshoot. Verapamil (10(-5) to 10(-4) M) depressed overshoot and plateau while slowing the final phase of repolarization. Verapamil (10(-4) M) depressed upstroke velocity and blocked excitability. While APDs recorded from these cultured cells are apparently longer than those reported by others for rat myocardial APDs, the values of all other electrophysiological parameters recorded are within the limits previously reported for normal rat myocardial tissue. These data indicate that adult rat myocardial cells maintained in tissue culture for 10–28 days possess electrophysiological properties and responses to pharmacological agents similar to adult rat myocardial tissue or undamaged freshly isolated cells.

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Effect of higenamine on action potential of ventricular myocardial cells

Journal of Electrocardiology ◽

10.1016/s0022-0736(85)80040-6 ◽

1985 ◽

Vol 18 (1) ◽

pp. 97-103 ◽

Cited By ~ 3

Author(s):

Guo Rui Yu ◽

Bin Yao Wang ◽

Dao Sheng Zheng ◽

Ming Xin Huang ◽

Bei Kun Gu ◽

...

Keyword(s):

Action Potential ◽

Myocardial Cells

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Loss of the Plateau of the Cardiac Action Potential in Hypertonic Solutions

The Journal of General Physiology ◽

10.1085/jgp.59.6.779 ◽

1972 ◽

Vol 59 (6) ◽

pp. 779-793 ◽

Cited By ~ 15

Author(s):

Kent Hermsmeyer ◽

Russell Rulon ◽

Nick Sperelakis

Keyword(s):

Guinea Pig ◽

Action Potential ◽

Surface Membrane ◽

Muscle Fibers ◽

Input Resistance ◽

Cell Diameter ◽

Hypertonic Solution ◽

Myocardial Cells ◽

Hypertonic Solutions ◽

T Tubules

The effect of hypertonicity on the electrical properties of vertebrate myocardial cells was studied in ventricular muscle fibers of guinea pig, cat, frog, and chicken. The latter two species do not have a T-tubule system, whereas the former two do. In hypertonic solutions (2 x isotonic) produced by addition of sucrose or excess of NaCl, cell diameter decreased and there was a slight hyperpolarization and decrease in action potential overshoot. In guinea pig and cat, the hypertonic solution caused a decrease in input resistance and the plateau of the action potential to disappear in some of the cells; contractions of the entire ventricle also became depressed. These effects were reversed by returning the muscle fibers to isotonic solution. Addition of 5 mM SrCl2 to the hypertonic solution also caused the plateau component and contraction to reappear. In frog and chick cells, loss of the plateau component and contraction never occurred in hypertonic solution, and input resistance increased. Urea and glycerol hyperosmolarity (2 x) caused no loss of the plateau component or contraction. If the frog and chicken ventricular, and guinea pig atrial myocardial cells (all of which lack T tubules) were to serve as an adequate control for possible effects of hypertonicity on the surface membrane and on contractile proteins, then the results suggest that swelling of the T tubules of mammalian myocardial cells leads to loss of the plateau component.

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