Mechanism of glucagon-induced intestinal secretion.

The effects of local intra-arterial glucagon infusion on transcapilary, lymphatic, and transmucosal fluid and protein fluxes were studied in autoperfused segments of cat ileum. The glucagon infusions resulted in a significant increase in intestinal blood flow, lymph flow, capillary filtration coefficient, capillary pressure, interstitial volume, and interstitial fluid pressure. Precapillary resistance and the pre-to-postcapillary resistance ratio decreased during the glucagon infusion. The transcapillary oncotic pressure gradient and the osmotic reflection coefficient were reduced, suggesting that capillary permeability is significantly increased with glucagon. Ultrastructural analysis of tissue samples acquired during the infusion of higher doses of glucagon indicates disruption of the mucosal membrane. An glucagon indicates disruption of the mucosal membrane. An alteration in mucosal structure is supported by the appearance of plasma proteins in the secreted fluid. The results of this study indicate that glucagon-induced intestinal secretion results from an alteration in capillary fluid balance, i.e., an increased capillary pressure and permeability.