Effects of H2O2 on membrane potential and [Ca2+]i of cultured rat arterial smooth muscle cells.
The effect of 1 mmol/l H2O2 was studied on the membrane potential and [Ca2+]i with microelectrodes and the fura-2 technique, respectively. H2O2 induced a biphasic increase in [Ca2+]i with a fast transient peak and a subsequent plateau. H2O2 also led to a biphasic hyperpolarization of the cells with a similar time course. This was followed by a slight depolarization after wash-out of H2O2. External Ca2+ free solutions and treatment with the Ca2+ ionophore A23187 (1 mumol/l) abolished the effect of H2O2 on [Ca2+]i and almost entirely reduced the effect on the membrane potential. Phenylephrine (10 mumol/l) or A23187 also induced very similar biphasic hyperpolarizations of the membrane as H2O2 which were fully reversible after wash-out. It is concluded that H2O2 hyperpolarizes the membrane by opening of Ca2+ dependent K+ channels.
Krippeit-Drews
P
P
Department of Physiology, University of Tübingen, FRG.
Haberland
C
C
Fingerle
J
J
Drews
G
G
Lang
F
F
D000818:Animals; D001158:Arteries / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D018999:Charybdotoxin; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D012604:Scorpion Venoms / Q000494:pharmacology
D012604:Scorpion Venoms; D018999:Charybdotoxin; D010656:Phenylephrine; D000001:Calcimycin; D006861:Hydrogen Peroxide; D002118:Calcium; D011224:Prazosin