Carbohydrate transport inMoniliformis dubius (Acanthocephala)

Summary

• 1. The body tissues of 32-day-old femaleMoniliformis dubius contained substantial levels of reserve carbohydrates. Glycogen accounted for approximately 24% of the tissue solids of worms from normally fed hosts; the non-reducing disaccharide trehalose (α-d-glucopyranosyl-{1→1}-α-d-glycopyranoside) was present at a concentration of 34 μmoles/ml tissue H₂O, and tissue levels of free glucose averaged 28 μmoles/ml tissue H₂O (Table 1).

• 2. Glycogen was present almost exclusively in the tissues of the body wall (table 2). The ethanol soluble sugars were partitioned between the body wall and the contents of the pseudocoelomic cavity in proportions approximating the percentage of the total body mass associated with each of these compartments (Table 2).

• 3. Exogenous¹⁴C-glucose was rapidly phosphorylated and subsequently incorporated into trehalose following its absorption (Table 3); this indicates that newly absorbed glucose did not enter directly into the endogenous glucose pools of the helminth body wall. Incorporation of radioactivity into glycogen was minimal.

• 4. Sequential incubation in³H- and¹⁴C-labelled glucose effected a partial separation of the metabolism of newly absorbed glucose from that of endogenous sugars (Tables 4 and 5). Ratios of activity from the two species of radioglucose among the major derivatives of absorbed glucose suggested that the tissue glucose pools derive not from free glucose but from the glucosyl moieties of trehalose (Table 5).

• 5. The data indicate that the glucose pools in the tissues ofM. dubius are physically separated from the tegumental epithelium, and they suggest that the accumulation of hexoses within these pools requires their incorporation into the disaccharide trehalose and its subsequent dismutation into free glucose units. the central role of trehalose in the carbohydrate metabolism ofMoniliformis is discussed, and a possible mechanism for the delivery of glucose moieties from trehalose into the tissue glucose pools by the action of a membrane-traversing “transporting trehalase” is considered.