Permeation and Membrane Transport in Animal Parasites: The Absorption of Glucose by Hymenolepis diminuta

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Abstract
A study of glucose uptake by Hymenolepis diminuta was made. Both extended time and short interval experiments were utilized in studying the effects of several physical, chemical and physiological factors. The Q10 values and the amount of energy necessary for placing glucose molecules in a reactive state suggest that metabolic energy might be involved in some manner in the permeation process. Although pH does not affect the absorption of glucose by this worm in short interval experiments, in extended time experiments an optimum of absorption occurs at pH 7.5. The concentration of glucose above 1.1 x 10-2 [image] has no effect upon the rate of uptake and the apparent Michaelis-Menten constant is 1.5 x 10-3 [image]. DNP in concentrations of from 10-5 [image] to 5 x 10-3 [image] reduces the rate of glucose absorption as does PCMB at a concentration of 4.4 x 10~3 [image]. Phlorizin in concentrations of 2.1 x 10-4 [image] and 6.3 x 10-4 [image] inhibits glucose absorption by H. diminuta. Lineweaver-Burk analysis yields results which can be interpreted as neither competitive nor noncompetitive inhibition. This inhibition by phlorizin acts at the surface of the worm. The rate of glucose absorption by H. diminuta is significantly increased 12 days after infection over rates at 8, 16, 20 and 90 days after infection. The size of the tapeworm has no effect upon the rate of permeation of glucose across its membrane.

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