Facilitated Diffusion and Exchange in the Absorption of Glucose by the Locust, Schistocerca gregaria (Forsk.)

Abstract

GLUCOSE absorption in the locust, Schistocerca gregaria (Forsk.), is largely confined to the mid-gut region of the alimentary canal, the uptake proceeding most rapidly from the mid-gut cæca¹. The rate of disappearance of glucose labelled with carbon-14 from the lumen of the mid-gut was found to be related to its rate of conversion to a disaccharide, trehalose, which accumulated in the hæmolymph. When the isolated alimentary canal was suspended in a relatively large volume of circulating poisoned saline, the disappearance of glucose was similar to that in the intact animal. On the basis of these observations it was suggested that the absorption of glucose might be achieved by diffusion across the gut wall, this process being facilitated by the rapid conversion to trehalose, which would tend to maintain a steep concentration gradient across the gut wall¹. This can be described as facilitated diffusion, in the sense that this term is used by Danielli².