Different regulatory mechanisms of Na+/ glucose transport in mouse ileum and jejunum

Abstract

Although glucose absorption in the proximal small intestine and its regulatory mechanisms have been extensively studied, less attention has been devoted to regulating glucose absorption in the distal small intestine. Ussing chamber technique was used to measure the glucose-induced short-circuit current in the isolated intestinal epithelium of mice to explore the regulation mechanism of glucose absorption in the ileum and compare it with those in the jejunum. Glucose induced a more pronounced short-circuit current in the ileum than in the jejunum and showed greater sensitivity to transporter inhibitors. Inhibition of Na⁺- dependent Ca²⁺, H⁺, or HCO₃^- transport reduced ileal glucose-induced current. 5-HT reduced ileal glucose-induced current, which could be restored by selective inhibitors of 5-HT4R, adenyl cyclase and protein kinase A. However, the extracellular Ca²⁺ and endoplasmic reticulum Ca²⁺ storage in the ileum did not regulate glucose transport as the jejunum did. Blockers of Ca²⁺ and K⁺ channels did not alter glucose-induced current in the ileum. In conclusion, the ileum has more pronounced glucose absorption, and its regulatory mechanisms significantly differ from those in the jejunum. The distal small intestine keeps efficient glucose absorption, but the regional differences of small intestinal segments in glucose absorption capacity may affect the effectiveness of oral medications, which needs attention.