Effects of superoxide anion on intracellular Ca2+ concentration in rabbit pulmonary arterial smooth muscle cells.
OBJECTIVE
To study the effect of superoxide anion on the Ca2+ homeostasis in smooth muscle cells isolated from the rabbit pulmonary artery.


METHODS
Intracellular Ca2+ concentration ([Ca2+]i) was investigated using cell suspension of freshly isolated smooth muscle cells from rabbit pulmonary artery (PASMC). Fura-2 fluorescent ratio obtained at 340 nm and 380 nm wave lengths was measured as an indicator of [Ca2+]i.


RESULTS
ATP 30 mumol.L-1 induced a transient increase in the ratio (Ca2+ transient). Thapsigargin, an inhibitor of sarcoplasmic Ca2+ ATPase, induced a phasic increase in the ratio due to Ca2+ leak from intracellular store sites, but not the sustained increase, thereby suggesting the absence of Ca2+ release-activated Ca2+ entry (CRAC) mechanism in PASMC. When PASMC were exposed to superoxide anion by the pretreatment with xanthine and xanthine oxidase (X/XO) for 30 min, sustained component of ATP-induced Ca2+ transient was elevated. The ratios at 5 and 10 min after ATP application (delta ratio5 min and delta ratio10 min) were increased from 0.091 +/- 0.022 to 0.149 +/- 0.048 (P < 0.05) and from 0.021 +/- 0.020 to 0.117 +/- 0.047 (P < 0.01), respectively. But, thapsigargin-induced [Ca2+]i transient was not affected by X/XO.


CONCLUSIONS
Superoxide anion makes ATP-induced Ca2+ transient sluggish, and does not affect Ca2+ leak pathway in PASMC.
Wang
Y P
YP
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan. ypwang@mail.shcnc.ac.cn
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D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002469:Cell Separation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005609:Free Radicals; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D011651:Pulmonary Artery / Q000166:cytology / Q000378:metabolism; D011817:Rabbits; D013481:Superoxides / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D019820:Xanthine / Q000494:pharmacology*; D014969:Xanthine Oxidase / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D005609:Free Radicals; D013481:Superoxides; D019820:Xanthine; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D014969:Xanthine Oxidase; D000252:Calcium-Transporting ATPases; D002118:Calcium