title: Vitamin C pretreatment attenuates hypoxia-induced disturbance of sodium currents in guinea pig ventricular myocytes.
abstract: As an important in vivo antioxidant, vitamin C is commonly used clinically to alleviate hypoxia-induced heart symptoms. To approach the protective mechanisms of vitamin C on hearts during hypoxia, we investigated the electrophysiological effects of vitamin C (1 mM: , pretreated before hypoxia) on Na(+) currents (including transient and persistent Na(+) currents) in guinea pig ventricular myocytes during hypoxia by the whole-cell and single-channel patch-clamp techniques. Whole-cell recordings showed that the mean current density of I (NaT) in the hypoxia group decreased from the control value of 40.2142 +/- 1.7735 to 27.1663 +/- 1.8441 pA/pF and current density of I (NaP) increased from 0.3987 +/- 0.0474 to 1.1854 +/- 01994 pA/pF (n = 9, P < 0.05 vs. control) at 15 min. However, when vitamin C was administered before hypoxia as pretreatment, I (NaT )and I (NaP )varied moderately (mean current density of I (NaT) decreasing from 41.6038 +/- 2.9762 to 34.6341 +/- 1.9651 pA/pF and current density of I (NaP) increasing from 0.3843 +/- 0.0636 to 0.6734 +/- 0.1057 pA/pF; n = 9, P < 0.05 vs. hypoxia group). Single-channel recordings (cell-patched) showed that the mean open probability and open time of I (NaP) increased significantly in both groups at hypoxia 15 min. However, the increased current values of the hypoxia group were still marked at hypoxia 15 min (n = 9, P < 0.05 vs. vitamin C + hypoxia group). Our results indicate that vitamin C can attenuate the disturbed effects of hypoxia on Na(+) currents (I (NaT) and I (NaP)) of cardiac myocytes in guinea pigs effectively.
authors.affiliation: Cardio-Electrophysiological Laboratory, Medical College, Wuhan University of Science and Technology, Wuhan, PR China.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhou
authors.forename: Ji-Hua
authors.initials: JH
authors.lastname: Ma
authors.forename: Pei-Hua
authors.initials: PH
authors.lastname: Zhang
authors.forename: An-Tao
authors.initials: AT
authors.lastname: Luo
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology*; D015687:Cell Hypoxia; D002478:Cells, Cultured; D005260:Female; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000502:physiology*; D013997:Time Factors
chemical_list: D000975:Antioxidants; D015222:Sodium Channels; D012964:Sodium; D001205:Ascorbic Acid