ANION AND CATION REQUIREMENTS FOR GLUCOSE AND METHIONINE ACCUMULATION BY HYMENOLEPIS DIMINUTA (CESTODA)

¹ Department of Biology, Rice University, Houston, Texas 77001

When incubated in 5 mM glucose in a buffered Krebs-Ringer saline for 60 min, Hymenolepis diminuta accumulated glucose to a steady state concentration of 25.5 mM in Cl-^-free saline, with either NO₃ -or CH₃COO^- as the replacement anion, glucose was accumulated by worms. H. diminuta incubated in 5 mM glucose in Nat⁺-free media, with choline as the replacement cation, did not accumulate glucose. Short term glucose influx (2 min) in H. diminuta was inhibited 96% in Na⁺-free media, and approximately 40% in Cl^--free media. The data support the hypothesis that glucose influx and accumulation in H. diminuta occurs through a Na⁺-dependent system similar to that proposed by the "ion-gradient hypothesis. "The data suggest further that glucose influx in H. diminuta may be anion-sensitive as well.

H. diminuta accumulated methionine when incubated in 2 mM methionine in normal saline, Na⁺-free media, or Cl^--free media, and short term methionine influx (2 min) in H. diminuta was unaffected by Na⁺ or C1^- deletion. Methionine influx and accumulation are not dependent on anion or cation differences (gradients) across the cell membranes and the energy necessary for solute accumulation must be derived from some source other than maintenance of these ion-differences.

Solute accumulation in H. diminuta was accompanied by significant water fluxes in some instances. Since the physical state of water and solutes within worms and the worms osmoregulatory capacities are unknown, the significance of these water fluxes is uncertain.