Ionic mechanisms of the depression of automaticity and conduction in the rabbit atrioventricular node caused by hypoxia or metabolic inhibition and protective action of glucose and valine.

The American Journal of Cardiology
M NishimuraY Watanabe

Abstract

The effects of hypoxia and a metabolic inhibitor, sodium cyanide (NaCN), on the spontaneous action potential and membrane current systems were studied in small preparations (0.2 x 0.2 x 0.1 mm) of rabbit atrioventricular node. When the PO2 of the superfusate was lowered from 500 to less than 20 mm Hg, all the preparations initially showed reductions in the spontaneous firing frequency (due to the decreased rate of diastolic depolarization) and maximal rate of depolarization, which were followed by a cessation of automatic activity with subsequent membrane hyperpolarization to -57 +/- 3 mV (n = 4). Voltage clamp experiments using double microelectrode techniques revealed that hypoxia reduced the slow inward current by 20 to 80% without affecting its inactivation kinetics. The delayed rectifying potassium current tail was also reduced or abolished by severe hypoxia, whereas the background outward current was greatly increased. The hyperpolarization-activated inward current was decreased by hypoxia. Similar changes in the spontaneous action potential and membrane currents were obtained on adding 0.1 to 0.5 mM NaCN to the superfusate under conditions of normal PO2. Hypoxia-induced suppression of automaticity was reversed completely...Continue Reading

References

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May 1, 1965·The Journal of General Physiology·D P MACLEOD, E E DANIEL

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Citations

Jan 29, 2013·Experimental Biology and Medicine·Kenneth J DrakeJohn P Wikswo
Jun 1, 1994·Journal of Cardiovascular Electrophysiology·Y Watanabe, M Watanabe
Mar 10, 2009·Journal of Pharmacological and Toxicological Methods·Chi-Kong YeungMansun Chan
Jun 20, 2017·BioMed Research International·Wei YaoZheng Wan

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