Figure 4. Concentration gradients in the para-cellular channels.
Differences in the glucose concentration between the apical and the basal ends of the sub-junctional para-cellular channels in rat (A) and human (B) are plotted against the rates of glucose absorption. The three lines in each panel show the relations when the vascular response is half normal (^), normal (•), and twice normal (▵). If transport of glucose were solely convective, the concentration gradient along the paracellular channel would be zero. Our equations predict small diffusion gradients that are proportional to glucose flux. The concentration of glucose reaching the abluminal surface of the villus capillaries (Cb) is normally within 15 % of its concentration in the subjunctional intercellular fluid (Ca).