Cholecystokinin 39 (CCK39)

The insulin-secretory response to CCK-39 and CCK-8 in the absence of other secretagogues was partially abolished by pretreatment with the cholinergic blocker methylatropine as well as with the beta-adrenoceptor blocker L-propranolol. Thus, this great insulin-secretory response to the two peptides seemed to be dependent on intact muscarinic and beta-adrenergic receptors. CCK-39 or CCK-8 administered in a threshold dose prior to half-maximal doses of D-glucose, the cholinergic agonist carbachol, or the beta-adrenergic agonist L-isopropylnoradrenaline (L-IPNA), respectively, displayed different influences on insulin release. CCK-39 potentiated glucose- as well as carbachol-induced insulin secretion, whereas it did not influence L-IPNA-induced insulin release. An equimolar dose of CCK-8, on the contrary, had no apparent effect on either glucose-, carbachol-, or L-IPNA-induced insulin release.