Permeation and Membrane Transport in Animal Parasites: On the Mechanism of Glucose Uptake by Hymenolepis diminuta

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Abstract
The study of glucose uptake by Hymenolepis diminuta was extended to include a consideration of possible mechanisms of transport. It was seen that if worms had been preincubated in either unlabelled glucose or galactose prior to incubation in C14 glucose, higher rates of uptake obtained than in cases in which preincubation in these sugars was omitted. Also, it was found that preincubation in fructose had no accelerating action. It was demonstrated that the glucose uptake by this tapeworm is a relatively stereospecific process. None of the following sugars and sugar derivatives had any inhibitory action on glucose uptake when added to the incubation medium: galactose, mannose, sorbose, fructose, 2-deoxyglucose, 2-deoxygalactose, 3-methyl glucose, glucosamine, xylose and glycerophosphate. A surface p-nitrophenyl phosphatase was demonstrated to occur in H. diminuta with a pH optimum of 9.5 and an apparent Michaelis constant of 3.2 x.10-3 M. It was shown that 1.6 x 10-3 M phlorizin had no effect on phosphatase activity, whereas 6.5 x 10-5 M ammonium molybdate inhibited this phosphatase. These data were compared with the effects of molybdate and phlorizin on glucose uptake by H. diminuta. The data are discussed in terms of their possible relation to mechanisms of glucose transport of this tapeworm.