Cytosolic calcium changes in cultured rat aortic smooth-muscle cells induced by oxyhemoglobin.
To clarify the mechanism of contractive effects in arteries caused by oxyhemoglobin, changes in the concentration of cytosolic calcium [( Ca++]i) before and after exposure to oxyhemoglobin were measured in vitro in cultured vascular smooth-muscle cells obtained from rat aorta. This was accomplished by preloading these cells with a fluorescent intracellular Ca++ probe fura-2/AM. Oxyhemoglobin induced a significant elevation of [Ca++]i in vascular smooth-muscle cells which was sustained for 10 minutes. This response was completely abolished by chelating extracellular calcium with ethyleneglycol-bis (beta-aminoethylether)-N,N'-tetra-acetic acid (EGTA). Oxyhemoglobin induced no accumulation of mass content of inositol 1,4,5-trisphosphate (IP3(1,4,5]. The oxyhemoglobin-induced elevation of [Ca++]i was not blocked by verapamil, a calcium antagonist. Serotonin induced a rapid, transient increase of [Ca++]i followed by a sustained elevation above baseline for 5 minutes. Additions of EGTA or verapamil had a small effect on the peak height of serotonin-induced [Ca++]i elevation, but the [Ca++]i level declined more quickly to the basal level in treated compared with control cells. These results indicate that oxyhemoglobin-induced [Ca++]i elevation is caused by the influx of extracellular calcium, which is independent of the verapamil-blocked voltage-gated calcium channel. The long-lasting high elevation of [Ca++]i caused by oxyhemoglobin suggests that oxyhemoglobin may contribute to the production of abnormal contractions and/or irreversible damage in vascular smooth-muscle cells.
Takenaka
K
K
Department of Neurosurgery, Gifu University School of Medicine, Japan.
Yamada
H
H
Sakai
N
N
Ando
T
T
Nakashima
T
T
Nishimura
Y
Y
Okano
Y
Y
Nozawa
Y
Y
D000818:Animals; D001011:Aorta; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D010108:Oxyhemoglobins / Q000502:physiology*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D007295:Inositol Phosphates; D010108:Oxyhemoglobins; D012701:Serotonin; D004533:Egtazic Acid; C062616:inositol 2,4,5-trisphosphate; D014700:Verapamil; D002118:Calcium