Published online by Cambridge University Press: 06 April 2009
Temporal changes in glucose transport capacity in excysted scoleces of Hymenolepis diminuta were examined. Assays involved incubation for 1 min in [3H]glucose after pre-incubation for 1 min to 8 h in saline. There were two abrupt increases in uptake velocity, a relatively small one between 15 and 75 min, and a large one between 5 and 6 h, during which the Vmax increased from 0·36 to 2·49 nmol/25 larvae/h. The second increase was unaffected when the pre-incubation saline contained 5 mM glucose, but it was completely blocked when the excysted larvae were pre-incubated in Ca2+-free saline. Abrupt glucose transport changes did not occur in intact cysticercoids or in scoleces when the substrate was [3H]leucine or [3H]uracil. Arrhenius plots (log V versus 1/temperature, 10–42 °C) were linear for intact cysticercoids, but were biphasic for both scoleces and adults with discontinuities at 20 ± 1 °C. Thus, ‘activation’ of the excysted scolex seemed to involve a specific, Ca2+ -dependent increase in number of glucose transporters functioning in the worm surface. The Arrhenius plots indicated that development in the final host does not involve a major change in lipid composition of the parasite's membranes.