Permeation and Membrane Transport in Animal Parasites: Further Observations on the Uptake of Glucose by Hymenolepis diminuta

Abstract

An extension of the study of glucose uptake by Hymenolepis diminuta supports the hypothesis that the process of permeation involved is an active one related to metabolic processes. Iodoacetate at concentrations of 1013 M and 3 x 10-4 M inhibits glucose uptake in 30-minute incubations; however, preincubation in iodoacetate was necessary in order to obtain inhibition of glucose uptake in 60-second incubations. The heating of worms reduced the glucose uptake rates to a level at which iodoacetate had no further depressing effect. DNP failed to inhibit the uptake of glucose by H. diminuta in 60-second incubations even after preincubation in the inhibitor. Sodium taurocholate inhibits glucose uptake by this worm in short interval experiments but only after preincubation in the taurocholate. A gradient of uptake activity was demonstrated; the anteriormost portion of the worm was found to take up glucose at a higher rate than were the posterior segments of worm tissue. The demonstration of apparent accumulation of glucose against a concentration gradient by H. diminuta was made in 60-second experiments. It was also shown that when placed in a salt solution favoring loss of glucose by diffusion, the worms lost no appreciable quantity of glucose. Possible advantages of an active glucose uptake process in the economy of the tapeworm are discussed.