Effects of intravenous infusions of cholecystokinin-8 and pentagastrin on plasma concentrations of insulin and glucagon in sheep

The effects of cholecystokinin-8 (cck-8) and pentagastrin on insulin and glucagon secretion were studied in conscious sheep. Intravenous infusions of ccx-8 (3 to 1000 pmol kg⁻¹ min⁻¹ for 30 minutes) induced a dose-dependent increase in plasma insulin, but did not alter plasma glucagon concentration. The threshold dose of ccx-8 for stimulation of insulin secretion was 10 to 30 pmol kg⁻¹ min⁻¹. Pentagastrin was infused intravenously at doses of 10 to 3000 pmol kg⁻¹ min⁻¹. The maximal dose of pentagastrin slightly stimulated insulin, but not glucagon, secretion. The insulin secretory activity of pentagastrin was only 1/300 that of ccx-8 on a molar basis. The threshold dose of ccx-8 for stimulation of insulin secretion was similar to that for exocrine pancreatic secretion obtained in earlier studies. In conclusion, ccx is a potential candidate as a physiological factor regulating insulin secretion in sheep.