AJP - Endocrinology and Metabolism, Vol 252, Issue 6 E727-E733, Copyright © 1987 by American Physiological Society
Effects of tetracaine on insulin release and calcium handling by rat pancreatic islets
S. M. el Motal, M. C. Pian-Smith and G. W. Sharp
The effects of tetracaine on insulin release and 45Ca2+ handling by rat
pancreatic islets have been studied under basal (2.8 mM glucose),
glucose-stimulated (5.6, 8.3, and 16.7 mM glucose), and
3-isobutyl-1-methylxanthine (IBMX)-stimulated conditions. Islets were
isolated by the use of collagenase and used either directly (freshly
isolated islets) or after a period under tissue culture conditions.
Tetracaine was found to stimulate insulin release under basal conditions,
to inhibit glucose-stimulated insulin release, and to potentiate insulin
release stimulated by IBMX. In studies on the mechanisms underlying these
effects, tetracaine was found to decrease glucose-stimulated net retention
of 45Ca2+ (by an action to block the voltage-dependent Ca channels) and to
mobilize Ca2+ from intracellular stores. These two actions form the basis
for the inhibition of glucose-stimulated insulin release, which depends
heavily on Ca2+ entry via the voltage-dependent channels and the synergism
with IBMX to potentiate release. No inhibition of IBMX-stimulated release
occurs because IBMX does not use the voltage-dependent channels to raise
intracellular Ca2+.
