Diabetes, Vol 37, Issue 10 1432-1437, Copyright © 1988 by American Diabetes Association
Stimulatory effects of cholecystokinin on isolated perifused islets inhibited by potent and specific antagonist L 364718 [corrected]
WS Zawalich, VA Diaz and KC Zawalich
Yale University School of Nursing, New Haven, CT 06536-0740.
The influence of L 364718 on islet responsiveness to sulfated
cholecystokinin (CCK-8S) was investigated. In islets whose
inositol-containing phospholipids were prelabeled during a 2-h incubation
period, subsequent exposure to L 364718 (1 nM) significantly impaired the
secretion of insulin usually noted in response to 200 nM CCK-8S in the
simultaneous presence of 7 mM glucose. A higher level of the antagonist (10
nM) completely abolished insulin secretion. L 364718 (1-10 nM) reduced the
efflux of 3H from myo-[2-3H]-inositol prelabeled islets in parallel with
the reduction in secretion. L 364718 (10 nM) significantly reduced the
accumulation of 3H-containing inositol phosphates usually noted with CCK-8S
addition. L 364718, at levels 10- to 100-fold greater than those necessary
to attenuate CCK-8S-induced insulin secretion, had no adverse effect on the
insulin secretory response of freshly isolated islets to 10 mM glucose
alone, 5 mM D-glyceraldehyde, 15 mM alpha-ketoisocaproate, or 50 ng/ml
gastric inhibitory polypeptide. L 364718 (1000 nM) had no adverse influence
on carbamylcholine (1 mM)-induced phosphoinositide hydrolysis. These
results establish L 364718 as a potent and highly selective antagonist of
cholecystokinin's stimulatory actions on beta-cells. Because of its
potency, selectivity, and oral effectiveness, in vivo studies with L
364718, aimed at unraveling the pleiotropic effects of CCK-8S on glucose
and insulin homeostasis, seem feasible.