Membrane transport of inositol by Hymenolepis diminuta (Cestoda)

The absorption of myoinositol by Hymenolepis diminuta involved diffusion that occurred at all substrate concentrations tested; at low substrate concentrations the mediated component predominated. The mediated process exhibited saturation kinetics with a Vmax and Kt of 0.011 mumoles/g of the ethanol-extracted dry wt/4 min and 0.0067 mM, respectively. Myoinositol transport was sensitive to changes in temperature, pH, and sodium ion concentration. D-Glucose was a noncompetitive inhibitor of myoinositol transport, but myoinositol had no effect on D-glucose absorption. Phlorizin interacted competitively with the myoinositol transport system. Various sugar alcohols and amino acids had no effect on myoinositol transport. These results indicate that a separate transport system exists in H. diminuta for myoinositol.