Distribution of Potassium, Sodium, and Chloride in Canine Purkinje and Ventricular Tissues

Vick, Robert L.; Hazlewood, Carlton F.; Nichols, Buford L.

doi:10.1161/01.res.27.2.159

Cited by 29 publications

(12 citation statements)

References 42 publications

(62 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Palfi anid associates (24) found that in vitro ouabain sensitivities of (Na+,K+)ATPase from detergent-treatedl homogeniates of calf Purkinije tissue and papillary mu.scle f'rom the same heart differed only slightly, with myocardiumil from papillary muscles showing 3-5% greater inhibition by ouabain concentrationis bracketing the IC,-value. In any event, these previous studies leave open the possibility that Purkinje fiber monovalenit cationl transport in vivo may be more sensitive to cardiac glycosides than is the case for myocardium, possibly due to intrinsic differences in ion conceintration and/or fluxes across the intact cell membrane (25,26), or that differences in drug access may occur in vivo.…”

Section: Resultsmentioning

confidence: 99%

Differing Sensitivities of Purkinje Fibers and Myocardium to Inhibition of Monovalent Cation Transport by Digitalis

Somberg¹,

Barry²,

Smith³

1981

J. Clin. Invest.

View full text Add to dashboard Cite

A B S T R A C T The extent of inhibition of monovalent cation active transport in Purkinje fibers and myocardium in response to toxic and inotropic doses of digitalis were studied in the dog to elucidate the factors underlying the different relative sensitivities of these tissues to the toxic arrhythmogenic effects of digitalis. Monovalent cation transport inhibition was assessed by measuring uptake of the K+ analog Rb+ in samples of myocardium and Purkinje fibers after in vitro ouabain exposure and after acute or chronic administration of digoxin in vivo. The active uptake of Rb+ was determined as the difference between total uptake and uptake in the presence of 1.0 mM ouabain. Mean active uptake of Rb+ by Purkinje fibers from control hearts was 1.62±0.11 (SEM) nmol/mg wet wt per 15 min, significantly greater than the value of 0.49±0.05 for myocardium (P < 0.001). Concentration-effect curves for inhibition of monovalent cation active transport by in vitro exposure to graded concentrations of ouabain showed that the concentration for half-maximal inhibition of monovalent cation transport, IC50, for Purkinje fiber transport was 0.4 ,M, significantly less than the value of 1.4 uM for myocardial samples. Dogs were given toxic doses of digoxin (0.3 mg/kg i.v.). At onset of sustained ventricular tachycardia, they were killed and monovalent cation transport measured in myocardial and Purkinje fiber samples. Active Rb+ uptake was inhibited by 44% in myocardial samples, whereas a significantly greater inhibition of 76% was noted in Purkinje fibers (P < 0.01). Similar data were obtained for both transmural myocardial biopsy samples and subendocardial trabecular samples obtained from regions adjacent to Purkinje fibers. Another group of dogs received a nontoxic dose of 0.02 mg/kg i.v. daily for 6 d. 'Myocardium showed a 17% reduction in Rb+

show abstract

Section: Resultsmentioning

confidence: 99%

Differing Sensitivities of Purkinje Fibers and Myocardium to Inhibition of Monovalent Cation Transport by Digitalis

Somberg¹,

Barry²,

Smith³

1981

J. Clin. Invest.

View full text Add to dashboard Cite

show abstract

“…Both values for the internal Na activity are substantially lower than most previous measurements of the total Na content of mammalian cardiac tissue. Using either flame photometry or radioactive-Na movements these measurements include: 39 mm in dog ventricle (Vick, Hazlewood & Nichols, 1970), 20-5 mm in guinea-pig auricle (Glitsch, Pusch & Venetz, 1976) and 32-7 mm in rabbit ventricle (Lee & Fozzard, 1975). Measurements on Purkinje fibres by Bosteels & Carmeliet (1972 a) produced a value of 25 mm.…”

Section: Discussionmentioning

confidence: 99%

The effects of external cations and ouabain on the intracellular sodium activity of sheep heart Purkinje fibres

Ellis¹

1977

The Journal of Physiology

313

219

View full text Add to dashboard Cite

SUMMARY1. The intracellular Na activity of sheep heart Purkinje fibres has been measured using recessed-tip Na+-sensitive glass micro-electrodes.2. The internal Na activity was 7-2 + 2-0 mm (mean + S.D., n = 32) at the normal external Na concentration, [Na]0, in these experiments of 140 mm (equivalent to an external Na activity of 105 mM). The equilibrium potential for Na across the fibre membrane was therefore approximately + 70 mV. 4. The removal of external K produced an easily reversible increase in the internal Na with an initial rate equivalent to a concentration change of 0-24 + 0 07 m-mole/min (mean + S.D., n = 8).5. Ouabain produced increases in the internal Na activity that were only very slowly reversible. The threshold concentration for producing an increase was approximately 10-7 M. 10. The relationship between internal Na and contractility is discussed.

show abstract

“…A more likely cause is a slow redistribution of Cl. The membrane is slightly permeable to Cl at membrane potentials within the range of -50 to -90 mV, 2 '" 28 and Cl is probably passively distributed across the membrane.…”

Section: Discussionmentioning

confidence: 99%

Two levels of resting potential in canine cardiac Purkinje fibers exposed to sodium-free solutions.

Wiggins¹,

Cranefield²

1976

Circulation Research

View full text Add to dashboard Cite

SUMMARY Canine cardiac Purkinje fibers exposed Co sodiumfree solutions containing 16 m,\i CaCL, 20 mM tetraethvlammonium chloride, 108 m\i tetramethylammonium chloride, and 2.7 m\i KCI may be quiescent at a resting potential of either -5 0 mV or -9 0 mV. The membrane potential of these fibers can be switched from -50 mV to -90 mV by a hyperpolarizing current pulse and from -90 mV to -50 mV by a depolarizing current pulse. The transition from -50 mV to -90 raV depends on a voltage-dependent increase in potassium conductance, that conductance being low at -50 mV and high at -90 mV. A reduction in potassium conductance causes the fiber to depolarize from -9 0 mV to -5 0 mV because of the presence of an inward current which apparently is carried mainly by Ca. Fibers that show a high resting potential cannot be excited except by depolarizing stimuli strong enough to move the membrane from -9 0 mV to a threshold potential of about -4 0 raV. Fibers that show a low resting potential are more easily excited and may show rhythmic activity sustained by afterpotentials that appear only if the low membrane potential is accompanied by a low potassium conductance. Slow changes in membrane potential also are seen; these changes may result from movements of chloride.CARDIAC PURKINJE FIBERS bathed in Na-free solutions can show two stable resting potentials, one near -90 mV and one near -50 mV.1 2 We now report that within a critical range of [KJ 0 the membrane potential can be shifted from either level to the other by the application of hyperpolarizing or depolarizing current pulses. This transition appears to be governed primarily by a voltage-dependent change in potassium conductance, that conductance being high at the -9 0 mV level and low at the -5 0 mV level. This phenomenon assumes special interest because cardiac fibers can produce two distinct types of propagated action potentials. One type, dependent on a rapid increase in sodium conductance, is abolished by voltage-dependent inactivation when the resting potential is low. The other type, called the slow response, depends on an increase in permeability which occurs at membrane potentials between -5 0 and +10 mV. Various cardiac arrhythmias arise in fibers in which a loss of resting potential causes the rapid upstroke to be replaced by the slow response.' The possibility that cardiac fibers are characterized not only by an ability to produce two types of action potential, but also by an ability to display the two levels of resting potential from which those action potentials can arise, is therefore intriguing. MethodsMongrel dogs of either sex weighing 15-20 kg were anesthetized with an intravenous injection of pentobarbital sodium (30 mg/kg). The heart was rapidly excised and immersed in Tyrode's solution (Table 1). Bundles of Purkinje fibers (false tendons) 4-12 mm long were removed from the right and left ventricles, placed in a tissue bath, and perfused with Tyrode's solution at 36-37 c C. Fibers which, had a membrane potential of less than -8

show abstract

Distribution of Potassium, Sodium, and Chloride in Canine Purkinje and Ventricular Tissues

Cited by 29 publications

References 42 publications

Differing Sensitivities of Purkinje Fibers and Myocardium to Inhibition of Monovalent Cation Transport by Digitalis

Differing Sensitivities of Purkinje Fibers and Myocardium to Inhibition of Monovalent Cation Transport by Digitalis

The effects of external cations and ouabain on the intracellular sodium activity of sheep heart Purkinje fibres

Two levels of resting potential in canine cardiac Purkinje fibers exposed to sodium-free solutions.

Contact Info

Product

Resources

About