SECRETIN RECEPTORS IN THE NEUROGLIOMA HYBRID CELL-LINE NG108-15 - CHARACTERIZATION AND REGULATION OF THEIR EXPRESSION

Secretin receptors in membranes from the neuroblastoma‐glioma hybrid cell line NG108‐15 were investigated by 125I‐secretin binding and adenylate cyclase activation. On both parameters the corresponding relative potencies of parent peptides were, respectively: secretin > helodermin > peptide histidine isoleucinamide = vasoactive intestinal peptide. With secretin analogs and secretin fragments, the order of potency for binding was: secretin = [Val5]secretin > [Ala2]secretin = [Ala11]secretin > [Ala4,Val5]secretin > [Ala4]secretin > [d‐Phe4]secretin > [d‐Phe2]secretin = secretin (2–27) > secretin (3–27) > secretin (7–27). Also, on adenylate cyclase, [d‐Phe4]secretin, [d‐Phe2]secretin, secretin (2–27) and secretin (3–27) were partial agonists while secretin (7–27) was ineffective. The differentiating agent N6,2′‐O‐dibutyryladenosine 3′,5′‐monophosphate (1 mM) increased the density of secretin receptors and secretin‐stimulated adenylate cyclase activity after a lag period of 4 h. After incubation for 24 h, receptor number and enzyme activity were increased 4‐ and 3‐fold, respectively. These effects were inhibited totally by 1 μg/ml cycloheximide and halved by 5 μg/ml actinomycin D. They were mimicked by 1 mM sodium butyrate but were not reproduced by either 8‐bromoadenosine 3′,5′‐monophosphate or the phosphodiesterase inhibitor rac‐4‐(3‐Butoxy‐4‐methoxybenzyl)‐2‐imidazolidinone. Copyright © 1990, Wiley Blackwell. All rights reserved