Effects of 5-hydroxytryptamine (serotonin) on the incorporation of 32P-inorganic phosphate into phospholipids in Hymenolepis diminuta (Cestoda)

5-Hydroxytryptamine (5-HT) (1,2 and 5 mM) significantly stimulated the incorporation of radioactive inorganic phosphate (32Pi) into phosphatidylinositol, phosphatidylethanolamine, phosphatidic acid and also total phospholipid fraction of Hymenolepis diminuta after one hour of incubation. Such effect was both time and concentration dependent. In the presence of 5-HT early labelling of phosphatidylinositol was observed. Also, the percentage stimulation by 5-HT was the highest in this fraction under all experimental conditions. The inorganic, organic, total and phosphatidylcholine-bound phosphate of H. diminuta incubated with 5-HT were not significantly different from those of the control under all incubation conditions. Results reported herein suggest that messenger molecules that are derived from phosphoinositides may be involved in the stimulatory mechanism of 5-HT in H. diminuta.