Effects of galactose, mannitol, glucose and alpha-methyl-D-glucoside on the incorporation of 32P-inorganic phosphate into phospholipids in Hymenolepis diminuta (Cestoda)

In the presence of glucose and galactose, the incorporation of radioactive inorganic phosphate (32Pi) into phosphatidylcholine of Hymenolepis diminuta was significantly lowered as compared to the control, whereas other phospholipids remained unaffected. alpha-methyl-D-glucoside, however, significantly lowered the amount of 32Pi incorporated into phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine and phosphatidic acid. Mannitol did not have any effect on the incorporation of 32Pi into the phospholipids of H. diminuta. The effect of glucose and alpha-methylglucoside on phospholipid metabolism was both time and concentration dependent. The inorganic, organic, total and phosphatidylcholine-bound phosphate of H. diminuta in the presence of various substrates were not significantly different from the control values under all incubation conditions. The results indicate that the observations made in the presence of external glucose, galactose and alpha-methylglucoside were due to their physical interaction with the transport mechanism in the tegumental membrane of H. diminuta and also their being subsequently metabolized in the cases of the former two hexoses.