The properties of caffeine- and carbachol-induced intracellular Ca2+ release in mouse bladder smooth muscle cells.
Freshly dissociated bladder smooth muscle cells of mice developed spontaneous, caffeine- (ICAF) and carbachol-induced (ICCh) currents under voltage-clamped conditions. Spontaneous currents, ICAF and ICCh were blocked with tetraethylammonium at 3 x 10(-4)-10(-2) M but were resistant to both charybdotoxin (10(-7)-10(-6) M) and iberiotoxin (10(-7)-10(-6) M). The reversal potential for each current indicated that K+ channels play a major role in the generation of each current. Both spontaneous currents and ICAF but not ICCh were abolished in nominally Ca2+-free and nicardipine (10(-6) M)-containing media. These results suggest that the activity of L-type voltage-sensitive Ca2+ channels is important in the generation and maintenance of spontaneous currents and ICAF but not ICCh. Ryanodine (10(-6) M) prevented spontaneous currents, ICAF and caffeine-induced [Ca2+]i elevation but not ICCh and carbachol-induced [Ca2+]i elevation, suggesting that the response of bladder smooth muscle cells to carbachol may involve a Ca2+ store distinct from that for caffeine. Pretreatment with carbachol suppressed ICAF to 22 +/- 7% (n = 7) and the caffeine-induced [Ca2+]i elevation to 25 + 3% (n = 6). Similarly, caffeine suppressed ICCh to 23 +/- 4% (n = 9) and the carbachol-induced [Ca2+]i elevation to 24 +/- 6% (n = 6).
Sugita
M
M
Department of Anesthesiology, Kumamoto University School of Medicine, Honjo, Japan.
Tokutomi
N
N
Tokutomi
Y
Y
Terasaki
H
H
Nishi
K
K
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D018679:Cholinergic Agonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005470:Fluorometry; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D001743:Urinary Bladder / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D018679:Cholinergic Agonists; D010726:Phosphodiesterase Inhibitors; D002110:Caffeine; D002217:Carbachol; D002118:Calcium