Effect of glucagon on esophageal motor function

Area of Science:

• Gastroenterology
• Endocrinology
• Pharmacology

Background:

• The lower esophageal sphincter (LES) plays a crucial role in preventing gastroesophageal reflux.
• Understanding factors that modulate LES pressure is important for managing esophageal disorders.

Purpose of the Study:

• To investigate the effect of exogenous glucagon on esophageal motor function, specifically LES pressure and esophageal peristalsis in humans.
• To determine if glucagon's effect on LES pressure is mediated by changes in serum insulin or glucose levels.

Main Methods:

• Manometric studies were conducted using an infused catheter system to monitor resting LES pressure.
• Intravenous pulse doses of glucagon were administered, and esophageal peristalsis was assessed.
• Blood samples were analyzed for glucagon, insulin, and glucose concentrations.
• Glucagon's effect was also evaluated during LES stimulation with pentagastrin.

Main Results:

• Glucagon caused a transient, significant decrease in LES pressure at high pulse doses (20 and 100 mug), leading to nonphysiological plasma glucagon levels.
• The reduction in LES pressure correlated with peak blood glucagon levels.
• Esophageal peristalsis was not demonstrably affected by glucagon.
• During pentagastrin-stimulated LES, glucagon induced significant transient decreases in LES pressure even at lower doses (1 mug/kg).

Conclusions:

• Exogenous glucagon exerts an inhibitory effect on LES pressure at pharmacologically relevant dosages.
• This inhibitory effect is independent of alterations in serum insulin or glucose.
• Glucagon's action on LES pressure appears to be a direct pharmacological effect.