Superoxide anion increases intracellular free calcium in human myometrial cells.
We investigated the effects of superoxide anion on the intracellular free calcium concentration ([Ca2+]i) in human cultured myometrial cells using a calcium-sensitive fluorescent dye, indo-1, and a digital imaging fluorescence microscopic system. Hypoxanthine (HX) plus xanthine oxidase induced a rise in [Ca2+]i in a manner dose-dependent on xanthine oxidase. The increase in [Ca2+]i in the absence of extracellular calcium ([Ca2+]ex) was 10% of that in the presence of [Ca2+]ex. Nifedipine, which blocks voltage-sensitive calcium channels, also reduced the increase in [Ca2+]i induced by HX-xanthine oxidase. Superoxide dismutase or superoxide dismutase plus catalase, which metabolizes superoxide anion, inhibited the effect of HX-xanthine oxidase on [Ca2+]i. The desensitization of the effect of superoxide anion on [Ca2+]i was investigated by pulsatile administration of HX and xanthine oxidase. Desensitization was observed on pulsatile administration of HX-xanthine oxidase at 2-min intervals. These data suggest that superoxide production may participate in uterine contraction via [Ca2+]i increase.
Masumoto
N
N
Department of Obstetrics and Gynecology, Osaka University Medical School, Japan.
Tasaka
K
K
Miyake
A
A
Tanizawa
O
O
D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003893:Desmin / Q000032:analysis; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D019271:Hypoxanthine; D007042:Hypoxanthines / Q000494:pharmacology*; D007700:Kinetics; D009215:Myometrium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009218:Myosins / Q000032:analysis; D009543:Nifedipine / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000494:pharmacology*
D003893:Desmin; D007042:Hypoxanthines; D013481:Superoxides; D019271:Hypoxanthine; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase; D009218:Myosins; D009543:Nifedipine; D002118:Calcium