Aerobic and anaerobic metabolism of larval and adult Taenia taeniaeformis. II. Hexose leakage and absorption; tissue glucose and polysaccharides

Abstract

Larval Taenia taeniaeformis leak both aerobically and anaerobically considerably larger amounts of glucose than adults. In larvae, the transition from glucose leakage to absorption takes place only when the concentration in external glucose concentration reaches a level of 100–200 mg%, while adult worms can extract large amounts of glucose from media containing initially only 12.5 mg% glucose. Comparison of determinations made by means of the glucose oxidase and the Hagedorn-Jensen techniques showed satisfactory agreement, proving that glucose, from a quantitative standpoint, is the most important carbohydrate leaked, although smaller amounts of nonglucose carbohydrates also are eliminated. The presence of galactose, mannose, or fructose in the medium does not prevent the glucose leakage, but can modify it. Hypotonie media do not induce increased glucose leakage, but maintaining adult worms in a sodium-free Tyrode solution increases the leakage to very high levels. However, there was no indication that, under the experimental conditions chosen, a glucose leakage against a concentration gradient occurred. Glucose absorption of adult worms is independent of the glucose concentration within the range of concentrations tested (initial concentrations: 12.5–200 mg%). Galactose absorption, however, is correlated with the concentration provided in the medium. Larval worms consume, in addition to large amounts of glucose and galactose, small amounts of mannose and probably fructose. There was no indication that adult worms absorb fructose, while the observations concerning mannose absorption were equivocal. Glucose consumption by adult worms is fairly independent of the osmolarity of the medium but is completely inhibited in a Na-free Tyrode solution. Phloridzin inhibits glucose absorption almost completely. Glucose absorption takes place against a concentration gradient. All observations are in accord with the assumption that glucose absorption by adult worms involves active transport mechanisms. It is not known whether the same situation prevails in larvae. Adult worms contain somewhat more free glucose in their tissues than the larvae. The glucose content of the adults increased during incubation in glucose-free medium, but much more during maintenance in glucose-containing media. No corresponding increase occurred in a Na-free solution, or when the medium contained phloridzin. The alkali-stable polysaccharides of both adult and larval worms are essentially glucose polymers with a small admixture of a substance that yields glucosamine and N-acetyl-glucosamine upon hydrolysis. Little indication of large scale glycogen synthesis was observed in adult worms incubated in various media, but glucose in the medium definitely has a sparing action on the polysaccharide stores.