Adrenaline inhibits depolarization-induced increases in capacitance the presence of elevated [Ca2+]i in insulin secreting cells.
Cell capacitance (Cm), cell conductance (Gm), access conductance (Ga) and membrane voltage (Vm) were measured simultaneously in insulin secreting cells using the dual frequency method. Depolarization and stimulation of the cells with secretagogues increased Cm. EGTA abolished the increase in [Ca2+]i and prevented the rise of Cm. Adrenaline inhibited the augmentation of Cm without lowering [Ca2+]i. In pertussis toxin pretreated cells adrenaline had no effect. Thus, stimulation of insulin secretion is accompanied by an increase in Cm. Inhibition of exocytosis by adrenaline occurs even in the presence of elevated [Ca2+]i, i.e. at a more distal step of exocytosis.
Lehr
S
S
Physiologisches Institut, Albert-Ludwigs Universität Freiburg, Abteilung II, Freiburg/Br, Germany.
Herbst
M
M
Kampermann
J
J
Greger
R
R
Ullrich
S
S
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D004837:Epinephrine / Q000494:pharmacology*; D005089:Exocytosis / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D037342:Pertussis Toxin; D051381:Rats; D014044:Tolbutamide / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D007328:Insulin; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D004533:Egtazic Acid; D014044:Tolbutamide; D037342:Pertussis Toxin; D005947:Glucose; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine; D004837:Epinephrine