Electrical activity alterations induced by chronic absorption of lindane (γ-hexachlorocyclohexane) trace concentrations in adult rat heart

2005 ◽  
Vol 83 (3) ◽  
pp. 243-251 ◽  
Author(s):  
Martin-Pierre Sauviat ◽  
Suzanne Bouvet ◽  
Gaston Godeau ◽  
Nicole Pages
Keyword(s):  
Left Ventricle ◽  
Action Potential ◽  
Electrical Activity ◽  
Heart Muscle ◽  
Female Rats ◽  
Resting Potential ◽  
Muscle Membrane ◽  
Papillary Muscles ◽  
Adult Rat ◽  
Trace Concentrations

The heart of adult rat offspring, born to mothers treated with trace concentrations of lindane (0.5 to 2 ppb) through a beverage and to mothers chronically treated with lindane (CL-T) with the same trace concentration, also through a beverage, during lactation and growth has a round shape and accumulates lindane. The left ventricle (LV) presents a hypertrophied area, atrophied papillary muscles, and unorganized collagen bundles and layers. These observations led us to study the electrical activity of their left ventricle papillary muscles (LVPM) by recording action potential using intracellular microelectrodes. CL-T shortened LVPM action potential duration (APD): 1 ppb shortened the plateau; 2 ppb shortened the plateau and the slow repolarizing phase. In CL-T (2 ppb) and untreated groups, low temperature (22 °C) decreased the resting potential and prolonged APD. TEA (tetraethylammonium; 1-2 mmol/L) partially lengthened CL-T (2 ppb lindane) APD. Quinidine (0.2 mmol/L) and E-4031 (10 nmol/L) prolonged CL-T APD, suggesting that the rapid delayed outward K+ current (IKr) was increased. Our results indicate the silent effects of chronic exposure to trace concentrations of lindane on the morphological and electrical activity of heart muscle. They demonstrate that chronic lindane treatment of female rats alters the tissue integrity and electrical activity in the LV of their offspring.Key words: heart muscle, membrane potential, lindane, K+ channel.

Electrophysiological Investigations of the Heart of Squilla Mantis

1964 ◽  
Vol 41 (4) ◽  
pp. 701-722
Author(s):  
HILARY F. BROWN
Keyword(s):  
Heart Muscle ◽  
Vital Staining ◽  
Heart Beat ◽  
Nerve Endings ◽  
Resting Potential ◽  
Muscle Membrane ◽  
Absolute Level ◽  
Local Contraction ◽  
Set Up ◽  
Junction Potential

1. The histology of the heart muscle of Squilla mantis is briefly described. Vital staining with methylene blue revealed only a sparse distribution of nerve endings on the muscle network. 2. Intracellular electrodes recorded from the muscle a multi-peaked junction potential at each heart beat. Each peak followed an impulse in the ganglionic nerve trunk burst. All the peaks were approximately the same height and none more than about three-fifths the height of the resting potential (average values for 10 hearts: resting potential, 51.5 mV; junction potential, 27.6 mV). 3. Inverted (negative-going) signals were never recorded just outside the muscle membrane suggesting that at all the points which were searched the membrane was acting passively. 4. Driving Squilla heart muscle via its nerve supply at 100 stimuli per second did not depolarize it by more than about 35 mV, nor would depolarizing pulses given directly to a fibre through an intracellular electrode set up any sort of current-generating activity in the membrane. 5. The magnitude of muscle contraction, measured locally using a microelectrode transducer, depended on the absolute level of the potential across the membrane, rather than on change of potential. 6. A directly applied electrotonus, similar in magnitude and duration to the nerve-induced junction potential, caused a local contraction of similar magnitude. 7. The recorded junction potential is therefore interpreted as the composite record of the electrotonus spreading within the muscle network from current initiated at relatively infrequent active points on the muscle membrane (the nerve endings) which passively depolarizes the rest of the membrane. 8. The junction potentials showed facilitation when the intervals between them were below 4 sec. At intervals less than 630 msec, they summed.

Effects of moderate hypoxia on premature action potentials of rabbit papillary muscle

1984 ◽  
Vol 62 (5) ◽  
pp. 596-599
Author(s):  
Julio Alvarez ◽  
Francisco Dorticós ◽  
Jesús Morlans
Keyword(s):  
Action Potential ◽  
Action Potential Duration ◽  
Action Potentials ◽  
Potassium Current ◽  
Maximum Rate ◽  
Resting Potential ◽  
Papillary Muscles ◽  
Premature Response ◽  
Coupling Interval ◽  
Control Response

Experiments were performed to study the effects of hypoxia on the characteristics of premature action potentials of rabbit papillary muscles. At normal resting potential, the duration of the premature action potential at the shortest coupling intervals was always greater than that of the control response. As the coupling interval was increased beyond 150 ms, the duration of the premature action potential regained control values. In cells depolarized to −70 mV by KCl, early lengthening of the premature response was attenuated. After 60 min of hypoxia, recovery of action potential duration at normal and reduced resting potentials was accelerated. The maximum rate of depolarization and its reactivation time constant were not affected by 60 min of hypoxia. It is suggested that intracellular free Ca is important in the control of action potential duration via the outward background potassium current.

scholarly journals Cat Heart Muscle in Vitro

1962 ◽  
Vol 46 (2) ◽  
pp. 189-199 ◽  
Author(s):  
Ernest Page
Keyword(s):  
Steady State ◽  
Heart Muscle ◽  
Potential Difference ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Papillary Muscles ◽  
K Concentration ◽  
Cat Heart ◽  
External K

The steady state transmembrane resting potential difference (Vm) has been measured in quiescent papillary muscles. Vm was determined as a function of the external K concentration in Cl and SO4 solutions and compared with the K equilibrium potential. Other measurements were made after replacement of external Na by choline, K by Rb and Cs, and Cl by SO4, CH3SO4, and NO3. Effects on Vm of albumin, temperature, and variation in internal K concentration are described.

The Water Balance of a Serpulid Polychaete, Mercierella Enigmatica (Fauvel)

1974 ◽  
Vol 60 (2) ◽  
pp. 351-370
Author(s):  
HELEN LE B. SKAER
Keyword(s):  
Action Potential ◽  
Electrical Activity ◽  
Muscle Cell ◽  
Cell Membranes ◽  
External Medium ◽  
Ionic Composition ◽  
Chloride Concentration ◽  
Chloride Ions ◽  
Resting Potential ◽  
Inward Current

1. The electrical activity of the two types of longitudinal muscles of an osmoconforming polychaete worm, Mercierella enigmatica, have been studied in media of widely varying osmotic and ionic composition. Activity persists practically unaltered in both types of muscle cell. 2. The possible effects of osmotically induced changes in cell volume on the ionic gradients across the cell membranes are considered. It is concluded that the normal gradients are unlikely to be maintained as a result of such changes. 3. The involvement of ion pumps in the maintenance of the normal gradients across the muscle cell membranes has been studied using specific and metabolic poisons. It is evident that the persistence of electrical activity in media of altered ionic content does not depend on the sodium-potassium exchange pump. 4. The ionic basis of the overshoot of action potentials recorded from cells of the small resting potential type has been studied. It is concluded that calcium ions but not sodium ions are responsible for the inward current although there is a component of the inward current carried by some other as yet unidentified ion. 5. Alterations in the external concentrations of chloride ions are found to alter both the height of the overshoot and the length of the action potential. 6. Profound alterations in the overshoot height are produced only when the normal ratio of calcium to chloride concentration in the external medium is altered. Possible mechanisms to explain these effects are discussed. 7. It is suggested that the stability of the action potential in the muscle cells of M. enigmatica, despite large fluctuations in the salinity of the external medium, depends on the constancy of the ratios between the concentrations of the ions in the fluids bathing the cells and not on the absolute concentrations of the ions.

Isolated myocytes from adult canine left ventricle: Ca2+ tolerance, electrophysiology, and ultrastructure

1983 ◽  
Vol 245 (5) ◽  
pp. H830-H839 ◽  
Author(s):  
K. Hewett ◽  
M. J. Legato ◽  
P. Danilo ◽  
R. B. Robinson
Keyword(s):  
Left Ventricle ◽  
Action Potential ◽  
Action Potentials ◽  
Single Cells ◽  
Resting Potential ◽  
High Yield ◽  
Intact Cells ◽  
Homogeneous Population ◽  
Ventricular Cells ◽  
Isolated Myocyte

We have developed a method for isolating single cardiac muscle cells in high yield (greater than 5 X 10(7) cells) from the canine left ventricle. Most of the myocytes are single cells with ultrastructural detail indistinguishable from intact ventricular myocardium, and more than 50% of the isolated cells remain elongated for at least 7 h in 0.5 mM calcium. Electrophysiological studies demonstrate that external potassium has a strong influence on repolarization in the isolated ventricular cells. Action potentials in [K+]o = 3.78 mM exhibit a positive over-shoot (greater than zero potential), but repolarization often arrests at congruent to -35 mV unless driven to more negative potentials by hyperpolarizing current. This phenomenon of two levels of resting potential is not observed at [K+]o = 5.78 mM. At the higher potassium concentration, values for maximum diastolic potential, amplitude, maximum rate of rise of phase 0, and action potential duration all are similar to those of intact ventricular muscle. However, the potential at the peak of the action potential plateau (phase 2) in the isolated myocyte is considerably more negative than that of intact myocardium. In addition, there is a conspicuous notch between phases 1 and 2 of the action potential in the isolated myocyte, whereas the notch is small or absent in intact myocardial action potentials. In summary, our method results in a preparation of stable, ultrastructurally and electrophysiologically intact cells, which should prove useful in studies requiring a large and homogeneous population of myocardial cells.

Electrophysiological properties of cultured adult rat ventricular cardiac muscle cells

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.

Experimental and theoretical ventricular electrograms and their relation to electrophysiological gradients in the adult rat heart

2009 ◽  
Vol 297 (4) ◽  
pp. H1521-H1534 ◽  
Author(s):  
Rodrigo Weber dos Santos ◽  
Anders Nygren ◽  
Fernando Otaviano Campos ◽  
Hans Koch ◽  
Wayne R. Giles
Keyword(s):  
Left Ventricle ◽  
Action Potential ◽  
Action Potential Duration ◽  
Left Ventricular ◽  
Large Mammals ◽  
Adult Rat ◽  
Rat Hearts ◽  
Mapping Techniques ◽  
Rat Ventricular Myocyte

The electrical activity of adult mouse and rat hearts has been analyzed extensively, often as a prerequisite for genetic engineering studies or for the development of rodent models of human diseases. Some aspects of the initiation and conduction of the cardiac action potential in rodents closely resemble those in large mammals. However, rodents have a much higher heart rate and their ventricular action potential is triangular and very short. As a consequence, an interpretation of the electrocardiogram in the mouse and rat remains difficult and controversial. In this study, optical mapping techniques have been applied to an in vitro left ventricular adult rat preparation to obtain patterns of conduction and action potential duration measurements from the epicardial surface. This information has been combined with previously published mathematical models of the rat ventricular myocyte to develop a bidomain model for action potential propagation and electrogram formation in the rat left ventricle. Important insights into the basis for the repolarization waveform in the ventricular electrogram of the adult rat have been obtained. Notably, our model demonstrated that the biphasic shape of the rat ventricular repolarization wave can be explained in terms of the transmural and apex-to-base gradients in action potential duration that exist in the rat left ventricle.

Action Potential Configuration in Heart Papillary Muscles from Female Rats in Different Thyroid States

1997 ◽  
Vol 105 (1) ◽  
pp. 58-65 ◽  
Author(s):  
S. Di Meo ◽  
P. de Martino Rosaroll ◽  
P. Venditti ◽  
M. Balestrieri ◽  
T. De Leo
Keyword(s):  
Action Potential ◽  
Female Rats ◽  
Papillary Muscles ◽  
Action Potential Configuration
Sign in / Sign up

Export Citation Format

Share Document