Alpha-adrenergic receptor stimulation during simulated ischemia and reperfusion in canine cardiac Purkinje fibers.

Hamra, Mary; Rosen, Michael R.

doi:10.1161/01.cir.78.6.1495

Cited by 35 publications

(23 citation statements)

References 37 publications

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“…It is assumed that, during the action potential, a K+ outward current is activated which counteracts the depolarization brought about by phenylephrine. The observed changes of membrane potential may be directly related to the arrhythmogenic properties of a-adrenoceptor agonists during ischaemia and reperfusion (Corr, Shayman, Kramer & Kipnis, 1981;Hamra & Rosen, 1988).…”

Section: U Jahnel and Othersmentioning

confidence: 99%

Depolarization‐induced influx of sodium in response to phenylephrine in rat atrial heart muscle.

Jahnel

Nawrath

Carmeliet

et al. 1991

The Journal of Physiology

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SUMMARY1. The effects of az-adrenoceptor stimulation on transmembrane potential, currents and ion fluxes were investigated in multicellular preparations and/or single cells obtained from the left atrium of rat hearts.2. In multicellular preparations, phenylephrine caused a concentration-dependent positive inotropic effect, an increase in action potential duration, and a decrease in resting potential; the effects were antagonized by phentolamine.3. In the presence of phenylephrine (100 ,umol/l), two levels of resting potential were observed when the preparations were, alternately, electrically stimulated or kept at rest (-74 +1 mV during activity and -62 + 4 mV at rest; means + S.E.M.; n = 9).4. In resting preparations, the depolarization in response to phenylephrine was eliminated in low-Na+ solution (12 mmol/l) and antagonized by tetrodotoxin (10 ,tmol/l).5. The phenylephrine-induced depolarization was also seen in nominally Ca2+-free solution and in the presence of (-)-devapamil (1 psmol/l). 11. In conclusion, we presume the following sequence of events in response to phenylephrine in rat atrial heart muscle. First, the stimulation of a,-adrenoceptors t To whom reprint requests and correspondence should be addressed.MS 7852

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Section: U Jahnel and Othersmentioning

confidence: 99%

Depolarization‐induced influx of sodium in response to phenylephrine in rat atrial heart muscle.

Jahnel

Nawrath

Carmeliet

et al. 1991

The Journal of Physiology

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“…These were coupled via an Ag-AgCl junction to a preamplifier as described previously [11]. The chamber was connected to ground and calibrated as described in Rosen et al [14].…”

Section: Generalmentioning

confidence: 99%

“…In other experi ments (where [K+]0 = 4 mM), standard techniques were used to stimulate the preparations [11].…”

Section: Generalmentioning

confidence: 99%

“…The model of ischemia used in this study has been described previously [11]. After equilibration in con trol Tyrode's solution, the fibers were superfused with a solution which mimics some of the components of ischemia (i.e.…”

Section: Experimental Protocolmentioning

confidence: 99%

“…a-Adrenergic stimulation during ischemia induces rhythmic activity in spontaneously beating adult fibers [11] and thus changes the normal adult response from inhibitory to excitatory. In normally polarized fibers, the inhibitory response is mediated by a pertussis toxin-sensitive substrate (a G; pro tein) acquired during development [12], while the excitatory response with ai stimulation during ischemia is eliminated with pertussis toxin pretreatment [13].…”

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confidence: 99%

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Developmental Differences in the Electrophysiological Response of Isolated Canine Purkinje Fibers to Adrenergic Stimulation during Simulated Ischemia

Fenrich¹,

Hamra²

1993

Dev Pharmacol Ther

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Developmental differences in adrenergic responsiveness may cause agerelated changes in the cellular response to ischemia. Standard microelectrode techniques were used in isolated young and adult canine Purkinje fibers to determine the effect of simulated ischemia ([K+]0 = 10 mM, pH 6.7, pO(2) <25 mm Hg) alone or with adrenergic stimulation on the rhythmic activity in spontaneously beating Purkinje fibers and on transmembrane potentials and delayed afterdepolarizations in paced Purkinje fibers (basic cycle length = 800-300 ms). The adrenergic agonists used were phenylephrine (5 X 10“8 M) and isoproterenol (1 x 10-6 M). For all automatic fibers studied, the control maximum diastolic potential in adults (-96 ± 1 mV, n = 37) and in the young (-98 ± 1 mV, n = 36) went to -62 ± 1 mV during ischemia in both groups and returned to -96 ± 2 mV with rcperfusion. The incidence of rhythmic activity (expressed as percent) during ischemia alone was similar at both ages: adults, 22%; young, 25%. The incidence of ectopic activity with phenylephrine superfusion during ischemia for adults was 63%, an effect blocked by prazosin (1 x 10~6 M) but not by propranolol (2 x 10-7 M); the incidence for the young was 25%. Isoproterenol caused ectopic rhythms in 86% of young fibers and 17% of adult fibers (p <0.05 young vs. adult). During reperfusion the return to control rhythm was slower in adults after ischemia alone or ischemia + a-adrenergic stimulation with phenylephrine. There were no age-related differences in the transmembrane potential response of paced fibers to ischemia or reperfusion, and there were no delayed afterdepolarizations with interruption of pacing at 800, 500, or 300 ms in either group. These data suggest that age-related differences in adrenergic responses alter the cellular response to an ischemic insult. To the extent that an ectopic beat may initiate an abnormal rhythm, these differences in sensitivity to adrenergic agonists may lead to developmental differences in arrhythmogenic potential during ischemia.

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Perioperative Maintenance of Normothermia Reduces the Incidence of Morbid Cardiac Events

Frank

Fleisher

Breslow

et al. 1997

JAMA

1,078

205

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Alpha-adrenergic receptor stimulation during simulated ischemia and reperfusion in canine cardiac Purkinje fibers.

Cited by 35 publications

References 37 publications

Depolarization‐induced influx of sodium in response to phenylephrine in rat atrial heart muscle.

Depolarization‐induced influx of sodium in response to phenylephrine in rat atrial heart muscle.

Developmental Differences in the Electrophysiological Response of Isolated Canine Purkinje Fibers to Adrenergic Stimulation during Simulated Ischemia

Perioperative Maintenance of Normothermia Reduces the Incidence of Morbid Cardiac Events

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