5-hydroxytryptamine induces transient Ca2+ influx through Ni2+-insensitive Ca2+ channels in rat vascular smooth muscle cells.
The effects of Ni2+, a non-selective cation channel inhibitor, on 5-hydroxytryptamine (5-HT)- and angiotensin II (Ang II)-induced intracellular Ca2+ dynamics in rat aortic smooth muscle cells were investigated. Ni2+ (1 mM) significantly inhibited the transient increase in intracellular Ca2+ concentration ([Ca2+]i) induced by Ang II (100 nM) in aortic smooth muscle cells, as measured using fura-2. However, Ni2+ did not suppress the transient increase in Ca2+ influx induced by 5-HT (10 microM), while significantly suppressed the sustained increase. Ca2+ influx evoked by high KCl (80 mM), thapsigargin (TG) (1 microM) or depletion of intracellular Ca2+ store was almost completely suppressed by Ni2+. Ni2+ had no effect on 5-HT-induced inositol triphosphate production and Ca2+ release from the intracellular store(s). These results suggest that 5-HT, but not Ang II, induces transient Ca2+ influx through Ni2+-insensitive Ca2+ channels, which are distinguishable from the voltage-dependent or store-operated Ca2+ channels.
Hirafuji
M
M
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Japan. hirafuji@hoku-iryo-u.ac.jp
Kawahara
F
F
Ebihara
T
T
Nezu
A
A
Tanimura
A
A
Minami
M
M
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009532:Nickel / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology*; D019284:Thapsigargin / Q000494:pharmacology
D015220:Calcium Channels; D000804:Angiotensin II; D012701:Serotonin; D011189:Potassium Chloride; D019284:Thapsigargin; D009532:Nickel; D002118:Calcium