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Functional and molecular characterization of CCK receptors in the rat pancreatic acinar cell line AR 4-2J

par Lambert, Monique;Bui, Ngoc Diem ;Christophe, Jean
Référence Regulatory peptides, 32, 2, page (151-167)
Publication Publié, 1991

Article révisé par les pairs

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Résumé :

Competitive inhibition binding studies on membranes from the rat pancreatic AR 4-2J cell line revealed the predominance (80%) of low selectivity CCk receptors (K(D) of 1 nM and 4nM for, respectively, CCK-8 and gastrin-17(I) (G-17(I))) over selective receptors (20% with a K(D) of 1 nM and 1 μM for respectively, CCK-8 and G-17(I)). Amylase secretion was stimulated by low concentrations of CCK-8, G-17(I) and CCK-4. G-17(I)-induced amylase secretion was unaffected by 100 nM of the selective peripheral CCK-A receptor antagonist L-364,718, suggesting that amylase hypersecretion followed non-selective CCK receptor activation, a function normally assumed by selective CCK-A receptors in rat pancreatic acini. Direct ultraviolet irradiation of AR 4-2J cell membranes preloaded with 125I-BH-CCK-33 or 125I(Leu)G(2-17)(I) resulted in covalent cross-linking with, respectively, a 90 kDa protein and a 106 kDa protein, both distinct from the 81 kDa CCK binding species revealed in normal rat pancreatic membranes. Gpp[NH]p increased the dissociation rate of CCK-8 and G-17(I) from AR 4-2J cell membranes, indicating a coupling of receptors with guanyl nucleotide regulatory protein(s) G. [32P]ADP-ribosylation of AR 4-2J cell membranes allowed to detect the presence of two G(s)α (the 50 kDa form predominating over the 45 kDa form) and one G(i)α (41 kDa). However, G(i) and G(s) may not be involved in gastrin stimulation of amylase secretion, as Bordetella pertussis toxin and cholera toxin pretreatment of cells did not suppress G-17(I)-dependent amylase secretion.