Plasma insulin response to intravenous administration of tetragastrin (C-terminal tetrapeptide amide of gastrin) in man

Abstract

Intravenous injection of 150 μg tetragastrin (Carbobenzoxy-L-tryptophanyl-L-methionyl-L-aspartyl-L-phenylalanine amide) resulted in a prompt and short-lived rise in plasma insulin concentration in healthy male volunteers. The concurrent infusion of glucose appeared to augment the plasma insulin response to the i.v. injection of tetragastrin. Intravenous injection of tetragastrin with glucose infusion produced a nearly normal rise in plasma insulin also in achlorhydric subjects. No significant difference was observed between the response of insulin to i.v. tetragastrin with glucose infusion in normal volunteers and achlorhydric subjects. Following the tetragastrin injection, plasma glucose increased slightly and free fatty acid tended to decrease. The slow infusion of 150 μg tetragastrin also tended to elicit a transient rapid rise in plasma insulin and a fall in free fatty acid without blood sugar change. The slow infusion of tetragastrin with glucose failed to augment the insulin response to the glucose infusion alone. Subcutaneous injection of 150 μg tetragastrin caused no changes in plasma insulin, glucose or free fatty acid.