Effects of CCK-8 on the cytoplasmic free calcium concentration in isolated rat islet cells.
The C-terminal octapeptide of cholecystokinin (CCK-8) is known to stimulate insulin secretion. We examined its effects on the cytoplasmic free calcium concentration ([Ca2+]IC) in isolated rat pancreatic islet cells. At 8.3 mM glucose and 1.28 mM Ca2+, CCK-8 (100 nM) rapidly increased [Ca2+]IC to a short-lived peak, whereafter the [Ca2+]IC, within 1.5 minutes, fell to values below baseline. CCK-8 also rapidly increased the [Ca2+]IC at 3.3 mM glucose and in a calcium deficient medium. However, either at low glucose or in the absence of extracellular Ca2+, the post-peak [Ca2+]IC did not fall below baseline levels. The CCKA receptor antagonist, L-364,718 (20 nM), inhibited the effects of CCK-8 on [Ca2+]IC. The results suggest that CCK-8 in islet cells liberates calcium from intracellular stores by activating CCKA receptors.
Fridolf
T
T
Department of Pharmacology, Lund University, Sweden.
Karlsson
S
S
Ahrén
B
B
D000818:Animals; D001570:Benzodiazepinones / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D002766:Cholecystokinin / Q000037:antagonists & inhibitors; D003593:Cytoplasm / Q000378:metabolism*; D020109:Devazepide; D004533:Egtazic Acid / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D005947:Glucose / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012844:Sincalide / Q000494:pharmacology*
D001570:Benzodiazepinones; D005456:Fluorescent Dyes; C049925:fura-2-am; D004533:Egtazic Acid; D002217:Carbachol; D002766:Cholecystokinin; D005947:Glucose; D020109:Devazepide; D012844:Sincalide; D002118:Calcium; D016257:Fura-2