Effect of intravenous somatostatin on jejunal absorption of glucose, amino acids, water, and electrolytes

Somatostatin has previously been reported to reduce plasma levels of sugars and triglycerides following oral test meals. This study was designed to answer the question as to whether or not somatostatin affects transport directly by inhibiting absorption across the mucosa of the small bowel. Steady-state perfusion experiments with either glucose- and amino acid-containing test solutions or a plasmalike electrolyte solution were carried out in the jejunum of healthy subjects. During the intestinal perfusion either saline (control) or somatostatin (8 μg/ kg/h) was infused for 90 min through a peripheral vein. Somatostatin infusion significantly reduced glucose absorption, and kinetic analysis revealed that this effect was mainly due to a reduction of V_max of glucose transport. Amino acid absorption (l-glycine and l-lysine) was also reduced by somatostatin infusion. Despite a significant decrease in undirectional water fluxes and calculated rate of water and urea diffusion, somatostatin did not affect net water or electrolyte absorption when the plasma-like electrolyte solution was perfused. These studies suggest that somatostatin inhibits glucose and amino acid absorption by a direct effect on the intestinal mucosa. Although the mechanism is unknown, we think that somatostatin most likely causes its effect by a selective reduction of functional mucosal surface area of the intestine.