The Journal of Neuroscience, July 15, 1999, 19(14):5741-5749
Potentiation of Quantal Catecholamine Secretion by Glibenclamide:
Evidence for a Novel Role of Sulphonylurea Receptors in Regulating the
Ca2+ Sensitivity of Exocytosis
S. C.
Taylor1,
E.
Carpenter1,
M. L.
Roberts2, and
C.
Peers1
1 Institute for Cardiovascular Research, University of
Leeds, Leeds LS2 9JT, United Kingdom, and 2 Department of
Physiology, University of Adelaide, Adelaide 5005, Australia
Electrochemical detection of quantal catecholamine release from
PC-12 cells revealed that glibenclamide, an inhibitor of ATP-sensitive K+ channels, potentiated
Ca2+-dependent exocytosis evoked by raised
extracellular [K+] and by exposure of cells to
caffeine. Glibenclamide was without effect on voltage-gated
Ca2+ currents, membrane potential, or rises of
[Ca2+]i evoked by either raised
extracellular [K+] or caffeine. The dependence of
K+-evoked secretion on extracellular
Ca2+ was shifted leftward in the presence of
glibenclamide, with a small increase in the plateau level of release,
suggesting that glibenclamide primarily increased the
Ca2+ sensitivity of the exocytotic apparatus.
Enhancement of secretion by glibenclamide was reversed by pinacidil and
cromakalim, indicating that the effects of glibenclamide were mediated
via an action on a sulfonylurea receptor. These results demonstrate
that sulfonylurea receptors can modulate
Ca2+-dependent exocytosis via a mechanism downstream
of Ca2+ influx or mobilization.
Key words:
glibenclamide; sulfonylurea; catecholamines; exocytosis; Ca2+; amperometry; KATP
channel; pheochromocytoma
Copyright © 1999 Society for Neuroscience 0270-6474/99/19145741-09$05.00/0