In the light of the strong potency of gastrin‐related peptides on pancreatic exocrine secretion in dog, we analyzed the binding properties of peptides related to cholecystokinin (CCK) and gastrin on dog pancreatic acini compared to guinea‐pig acini. Moreover, we determined apparent molecular masses of photoaffinity labelled CCK/gastrin receptors in the two models. Using the CCK radioligand, receptor selectivity towards CCK/gastrin agonists and antagonists was found to be lower in dog acini than in guinea‐pig acini. Performing the binding with CCK and gastrin radioligands in combination with N2,O2′‐dibutyryl‐guanosine 3′,5′‐monophosphate, revealed that in dog acini there exist two different sub‐classes of CCK/gastrin receptors having high and low selectivity, the latter ones being able to bind gastrin with high affinity (Kd= 2.1 nM). SDS‐PAGE analysis of covalently cross‐linked receptors using several photosensitive CCK and gastrin probes of different peptide chain lengths demonstrated that in guinea‐pig, CCK peptides bound to a 84‐kDa component whereas in dog pancreas, CCK and gastrin peptides bound to three distinct molecular species (Mr∼ 78000, 45000, 28000). Performing crosslinking in the presence of 1 μM CCK indicated that a 45‐kDa protein is the putative CCK/gastrin receptor in dog pancreas. Our results support the concept of heterogeneity of CCK/gastrin receptors.
increased accumulation of putrescine, spermidine and spermine, and that a-Difluoromethyl ornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), can specifically inhibit caerulein induced pancreatic hypertrophy. These data lend further support to the involvement of ODC and polyamines in induced pancreatic growth, but up to now the study of the mechanisms involved is restricted by the lack of a suitable in vitro model.In the present study using the AR42J cell line in which CCK receptors and stimulation of amylase release by CCK peptides have already been demonstrated,5 we investigated the presence of gastrin
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