Effects of KSG-504, a New Cholecystokinin-A-Receptor Antagonist, on Pancreatic Exocrine and Endocrine Secretions in Rats

The effects of KSG-504 ((S)-arginium (R)-4-[N-(3-methoxypropyl)-7V-pentylcarbamoyl]-5-(2-naphthylsulfonyl) pentanoate monohydrate), a new cholecystokinin (CCK)-A-receptor antagonist, on pancreatic exocrine secretion in anesthetized rats and endocrine secretion in conscious rats were studied. Intravenous injection of KSG-504 inhibited the pancreatic amylase output stimulated by intravenous infusion of CCK-8 in a dose-dependent manner (ED50: 18 μg/kg/min). Moreover, KSG-504 significantly reduced the CCK-8-stimulated increases in pancreatic juice volume and outputs of protein, trypsin and lipase. Intraduodenal infusion of casein increased the plasma CCK concentration and the pancreatic amylase output. KSG-504 significantly inhibited the pancreatic amylase output stimulated by casein. Pancreatic juice volume and bicarbonate output were significantly stimulated by intravenous infusion of secretin, but were not changed by KSG-504. When pancreatic exocrine secretion was stimulated by secretin plus CCK-8, KSG-504 suppressed the increases in juice volume and bicarbonate output to the level stimulated by secretin alone. Basal pancreatic amylase output was decreased by KSG-504. KSG-504 decreased the level of plasma immunoreactive insulin (IRI) stimulated by glucose plus CCK-8, but had no effect on IRI stimulated by glucose alone and the basal IRI. These in vivo studies suggest that KSG-504 has significant inhibitory effects both on the pancreatic exocrine and endocrine secretion stimulated by CCK, but has no effect on the exocrine secretion stimulated by secretin.