Effect of 5-hydroxytryptamine on intracellular calcium dynamics in cultured rat vascular smooth muscle cells.
The present study elucidated the precise mechanism of 5-hydroxytryptamine (5-HT)-induced increase of intracellular Ca2+ concentration ([Ca2+]i) in cultured vascular smooth muscle cells isolated from rat aortic media. [Ca2+]i was measured using fluorescent Ca2+ indicator, fura-2. 5-HT caused a dose-dependent increase in [Ca2+]i, which was completely inhibited by ketanserin. alpha-Methyl-5-HT had an equipotent effect to 5-HT. Diltiazem at 10 microM partially suppressed the 5-HT-induced increase in [Ca2+]i. 5-HT also augmented Mn2+ influx, when monitored by Mn2+ quenching of fura-2 fluorescence. When extracellular Ca2+ (1.3 mM) was removed, a decrease in resting level and a small, transient increase in [Ca2+]i were observed. 5-HT stimulation also induced an increase in the production of inositol triphosphate. 5-HT-induced increase in [Ca2+]i was significantly, but partially inhibited by staurosporin and H-7. Phorbol 12-myristate 13-acetate induced an increase in [Ca2+]i, which was abolished by removal of extracellular Ca2+. 5-HT-induced increase in [Ca2+]i was not affected by the pretreatment with pertussis toxin (PTX), and was not accompanied by a change in cyclic AMP content. These results suggest that, in cultured rat aortic smooth muscle cells, 5-HT increases [Ca2+]i via 5-HT2 receptor subtype by inducing influx of extracellular Ca2+ partially through L-type voltage-dependent Ca2+ channel, as well as by mobilizing Ca2+ from its intracellular stores. Activation of protein kinase C may be positively involved in the regulatory mechanism of Ca2+ influx, but PTX-sensitive G protein and cyclic AMP seem to be not involved.
Hirafuji
M
M
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Japan.
Nezu
A
A
Kanai
Y
Y
Ebihara
T
T
Kawahara
F
F
Tanimura
A
A
Minami
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D011493:Protein Kinase C / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*
D015220:Calcium Channels; D007295:Inositol Phosphates; D011985:Receptors, Serotonin; D012701:Serotonin; D000242:Cyclic AMP; D011493:Protein Kinase C; D002118:Calcium