Noradrenergic inhibition and voltage-dependent facilitation of omega-conotoxin-sensitive Ca channels in insulin-secreting RINm5F cells.
We found that, besides dihydropyridine-sensitive Ca channels, insulin-secreting RINm5F cells also contain a minority (15-25%) of omega-conotoxin (omega-CgTx)-sensitive channels that show a high-affinity binding to [125I] omega-CgTx (Kd 51 pM). Noradrenaline (NA, 10 microM) slows down Ca-channel activation in these cells and produces a sizeable reduction of Ca currents that is relieved by strong pre-conditioning depolarizations (facilitation). The action of NA is mimicked by intracellular application of GTP-gamma-S and is prevented by pertussis toxin (PTX) or by cell pre-incubation with omega-CgTx. This suggests specific noradrenergic inhibition of omega-CgTx-sensitive Ca channels that is modulated by membrane potentials and PTX-sensitive G-protein activation.
Aicardi
G
G
Department of Anatomy and Human Physiology, Torino, Italy.
Pollo
A
A
Sher
E
E
Carbone
E
E
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007340:Insulinoma; D007700:Kinetics; D009638:Norepinephrine / Q000494:pharmacology*; D010190:Pancreatic Neoplasms; D010456:Peptides, Cyclic / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D007328:Insulin; D010456:Peptides, Cyclic; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D020866:omega-Conotoxin GVIA; D009638:Norepinephrine