Aerobic and anaerobic metabolism of larval and adult Taenia taeniaeformis. IV. Absorption of glycerol; relations between glycerol absorption and glucose absorption or leakage

1. 1. Both larval and adult Taenia taeniaeformis absorb large amounts of glycerol from the environment. The larvae consume more glycerol aerobically than anaerobically, a difference lacking in the adults. 2. 2. Glycerol in the medium does not prevent glucose leakage completely, but in the larvae an inverse relationship between concentration of environmental glycerol and extent of glucose leakage exists. 3. 3. When immersed in a mixture of glycerol and glucose both larvae and adults consume more of the former than the latter compound. Simultaneous availability of both substrates leads to a greater influx of organic material into the worm bodies than if only one of the compounds is available. There is little, if any, indication of mutual inhibition of absorption. 4. 4. Only few metabolic inhibitors or changes in environmental conditions lead to significant reductions in the rate of glycerol uptake. Most consistent inhibition is observed upon immersion of the worms into a Na +-free Tyrode's solution, but even in this case glycerol absorption is much less inhibited than glucose uptake. Phloridzin which also completely inhibits glucose uptake is entirely without effect on glycerol absorption. 5. 5. Lowering the temperature from 37 ° to 7 °C leads to considerable reduction of glycerol uptake, to increases in the tissue levels of glycerol, to increased glucose leakage, and thus to a decrease in the tissue level of glucose. 6. 6. The glycerol consumption of larval worms is more dependent on the environmental glycerol concentration than that of the adults. 7. 7. It seems probable that at very low environmental concentrations of glycerol absorption involves active transport mechanisms, while at higher concentrations diffusion, probably facilitated diffusion, appears to prevail.