Norepinephrine and potassium fluxes in cardiac Purkinje fibers

Vassalle, Mario; Barnabei, O.

doi:10.1007/bf00587747

Cited by 81 publications

(44 citation statements)

References 24 publications

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“…In the present study solutions containing rather less elevated K + and a somewhat lowered Na + plus epinephrine, and solutions or agar containing high K + and epinephrine induced depression of conduction velocity, slow upstrokes and block at critical regions. It is known that a combination of high K + and epinephrine produces slowly propagated potentials (4) and that epinephrine never produces phase 4 depolarization or spontaneous activity in the presence of high K + (3)(4)(5). The ways in which the necessary level of slow conduction might appear in the whole heart have been discussed previously (2).…”

Section: Discussionmentioning

confidence: 99%

Slow Conduction and Reentry in the Ventricular Conducting System

Wit

Hoffman

Cranefield

1972

Circulation Research

202

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Depression of excitability and responsiveness provoked by the action of high K 1^ and epinephrine on short bundles of excised canine Purkinje fibers yields reentrant excitation. An impulse entering a depressed area undergoes marked slowing of conduction; the impulse then may continue forward while also returning through the pathway by which the initiating impulse entered the depressed area. The impulse may be delayed or blocked in either the forward or the retrograde direction. The reentrant excitation can occur in the absence of premature excitation. Various methods of depression of excitability produce return extrasystoles in Purkinje fibers. The common factor is very slow conduction which depends upon the abolition of the fast upstroke and the appearance of a low-voltage, slowly propagated action potential that is readily blocked. KEY WORDSecho beats ventricular bigeminy myocardial ischemia ventricular fibrillation coupled extrasystoles reciprocal rhythm mechanisms of arrhythmias myocardial infarction ventricular tachycardia• That reentry of excitation within the ventricle or the ventricular conducting system might cause extrasystoles and other disturbances of ventricular rhythm has been a widely held hypothesis for many decades. Yet it has proved surprisingly difficult to evoke unequivocal reentry under experimental con-•ditions. Doubt has also been expressed that The research was supported by a grant-in-aid from the New York Heart Association (to Dr. Cranefield) and by a grant from the National Institutes of Health (Grant HE 11994-03). Dr. Wit is a Senior Investigator of the New York Heart Association and a Fellow of the John Polachek Foundation for Medical Research.Received May 10, 1971. Accepted for publication November 1, 1971. reentry could arise from slow conduction, which has led to efforts to obtain reentry by methods that shorten the refractory period. We have recently shown that short segments of depressed fibers of the ventricular conducting system may show very slow conduction, one-way conduction, summation, and inhibition (1, 2). Those properties are sufficient to create reentry, and we have now demonstrated reentry secondary to slow conduction. We report elsewhere (3) that the presence of slow conduction and of areas of one-way block make possible circus movement around loops of Purkinje fibers 20 to 30 mm in length. In the present article we report on a form of reentry seen in short depressed segments of bundles of Purkinje fibers (false tendons) that appear under the dissecting microscope at a magnification of 25 X as unbranched. Although these bundles contain more than one

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Section: Discussionmentioning

confidence: 99%

Slow Conduction and Reentry in the Ventricular Conducting System

Wit

Hoffman

Cranefield

1972

Circulation Research

202

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“…Received July 12, 1976; accepted for publication October 15, 1976. In 1971 Posner and Vassalle 3 and Vassalle and Barnabei 4 reported that low concentrations of norepinephrine decrease 42 K uptake by canine Purkinje fibers but higher concentrations increase 42 K uptake. They concluded that the reduction of the K + uptake at low norepinephrine concentrations is an a-adrenergic function mediated through depression of the Na + -K + exchange pump.…”

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confidence: 98%

“…This suggestion is consistent with a view that not all catecholamine-induced effects on the cardiac cell are mediated by the a-and /3-receptors. For example, Vassalle and Barnabei 4 have demonstrated that although norepinephrine stimulates the active transport of potassium this action can be dissociated from norepinephrineinduced increases in automaticity. Stimulation of active transport -if it results in an increase in the intracellular potassium concentration -might well induce an increase in membrane potential.…”

Section: The Transmembrane Action Potentialmentioning

confidence: 99%

Effects of adrenergic amines on electrophysiological properties and automaticity of neonatal and adult canine Purkinje fibers: evidence for alpha- and beta-adrenergic actions.

Rosen¹,

Hordof²,

Ilvento³

et al. 1977

Circulation Research

131

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SUMMARY We determined age-related differences in automaticity and responsiveness of cardiac Purkinje fibers from adult and neonatal dogs to graded concentrations of epinephrine, isoproterenol, and phenylephrine. Purkinje fibers were studied with standard microelectrode techniques during superfusion with Tyrode's solution at 37°C. Control spontaneous rates fur adults and neonates did not differ significantly. There was a biphasic response to all agonists such that rate decreased at low and increased at high concentrations. The decrease was greater with phenylephrine and epinephrine than with isoproterenol. The increase in rate was greater with isoproterenol and epinephrine than with phenylephrine. Propranolol shifted the dose-response curves downward and to the right for all agonists; phentolamine, shifted the curves upward and to the left. Epinephrine and isoproterenol dose-response curves for the neonates were upward and to the left of those for adults. Phenylephrine curves were identical for adults and neonates. Thus there are a-and /3-adrenergic effects on Purkinje fiber automaticity; the former decrease and the latter increase rate. Furthermore, the effects on automaticity of /3-adrenergic amines are greater in the neonates than in the adult.IN THE present study we determined the effects of adrenergic amines on automaticity and action potential (AP) characteristics of Purkinje fibers from neonatal and adult dogs. A number of recent studies have indicated that adrenergic amines have a and /3 agonistic effects on cardiac fibers. Ledda et al. 1 showed that phenylephrine, which has a high ratio of a to /3 agonistic activity, increases AP duration of sheep Purkinje fibers. Giotta et al.2 observed that isoproterenol decreases the duration of the Purkinje fiber AP, an action blocked by propranolol but not by phentolamine. They also found that norepinephrine decreases AP duration in the presence of phentolamine and increases AP duration in the presence of propranolol. These results led the authors to suggest that prolongation of the AP duration is an a-adrenergic effect and that its shortening is a /3-adrenergic effect.

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“…However, the effects of /1-stimulation on Na+-K+ transport remain a matter of controversy. Some investigators have observed a stimulation of transporter activity (Vassalle & Barnebei, 1971;Falk & Cohen, 1982;Desilets & Baumgarten, 1986) while others have not (Gadsby, 1983; Gadsby, 1990; Bielen, Glitsch & Verdonck, 1991). Alternatively, Gadsby (1983) and Glitsch, Krahn, Pusch & Suleymanian (1989) suggested that fl-activation increases K+ conductance, causing K+ accumulation in the narrow extracellular spaces, thus indirectly stimulating Na+-K+ transport.…”

Section: Introductionmentioning

confidence: 99%

Isoprenaline, Ca2+ and the Na(+)‐K+ pump in guinea‐pig ventricular myocytes.

Gao

Mathias

Cohen

et al. 1992

The Journal of Physiology

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SUMMARY1. The whole-cell patch clamp technique was employed to study the effects of the ,f-agonist isoprenaline (ISO) on the Na+=K+ pump current, Ip, in acutely isolated ventricular myocytes from guinea-pig hearts. Propranolol, a ,l-adrenergic antagonist, was used to demonstrate that all of the effects of ISO, stimulatory or inhibitory, are mediated by fl-receptors. (Giles, Nakajima, Ono & Shibata, 1989; Duchatelle-Gourdon, Hartzell & Lagrutta, 1989) helps prevent action potential lengthening and allows an increase in heart rate even in the presence of increased calcium current. Further, fl-stimulation will compensate for the effects on Ip of either hypokalaemia or digitalis toxicity, and so reduce the expected rise in both [Na+]

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Norepinephrine and potassium fluxes in cardiac Purkinje fibers

Cited by 81 publications

References 24 publications

Slow Conduction and Reentry in the Ventricular Conducting System

Slow Conduction and Reentry in the Ventricular Conducting System

Effects of adrenergic amines on electrophysiological properties and automaticity of neonatal and adult canine Purkinje fibers: evidence for alpha- and beta-adrenergic actions.

Isoprenaline, Ca2+ and the Na(+)‐K+ pump in guinea‐pig ventricular myocytes.

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