Pentagastrin is a synthetic polypeptide and cholecystokinin-2 (CCK2) receptor agonist. It binds selectively to CCK2 receptors in guinea pig brain over CCK1 receptors in rat pancreas (IC50s = 11 and 1,100 nM, respectively). Pentagastrin increases calcium influx and polyphosphoinositide turnover in rat GH3 pituitary cells (EC50s = 23 and 3.9 nM, respectively). It also increases histidine decarboxylase activity in mucous- and endocrine cell-enriched isolated rabbit fundic mucosal cells (EC50 = 2.9 nM). Pentagastrin induces contraction of isolated pig ileum smooth muscle cells in vitro (EC50 = 30 pM). It increases gastric acid and pepsin secretion in conscious cats in vivo (ED50s = 1.29 and 57.3 nmol/kg2 per hour, respectively). Formulations containing pentagastrin have previously been used as a diagnostic aid to evaluate gastric acid secretory function.
