Noradrenaline inhibition of Ca2+ channels and secretion in single patch-clamped insulinoma cells.
Noradrenaline effects on voltage-operated calcium channels and exocytosis were studied, for the first time, in single patch-clamped RINm5F insulin-secreting cells. Noradrenaline, despite small and variable inhibition of calcium currents, strongly inhibited the increase in membrane capacitance (a measure of exocytosis) stimulated by both step depolarizations and the calcium ionophore, ionomycin. Noradrenaline similarly inhibited KCl- and ionomycin-induced [3H]serotonin release from RINm5F cell populations. Noradrenaline effects were mediated by PTX-sensitive G proteins. Noradrenaline inhibitory effects on secretion are, therefore, mainly exerted downstream from Ca2+ influx.
Sher
E
E
Békésy Laboratory of Neurobiology, Pacfic Research Center, University of Hawaii, Honolulu 96822, USA.
Codignola
A
A
Rogers
M
M
Richmond
J
J
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects*; D004594:Electrophysiology; D005089:Exocytosis / Q000187:drug effects*; D007340:Insulinoma / Q000378:metabolism*; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000378:metabolism; D014407:Tumor Cells, Cultured; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D015220:Calcium Channels; D007476:Ionophores; D010566:Virulence Factors, Bordetella; D012701:Serotonin; D015759:Ionomycin; D011189:Potassium Chloride; D002118:Calcium; D009638:Norepinephrine