title: Diacylglycerol and phosphatidate production and the exocytosis of the sperm acrosome.
abstract: We have investigated the production of diacylglycerol (DAG) and phosphatidate (PtdOH) during the exocytosis of the sperm acrosome. Ram spermatozoa treated with Ca2+ and the ionophore A23187 experienced a rapid breakdown of the polyphosphoinositides (PPIs), and a rise in [32P]Pi-labelled PtdOH and DAG mass; PtdOH mass, however, was unaffected. Treatment with Ca2+/A23187 and the DAG kinase inhibitor R59022 resulted in a dose-dependent increase in DAG mass and a concomitant decrease in [32P]PtdOH; such treatment showed a dose-dependent stimulation of acrosomal exocytosis. Pre-incubation with exogenous PtdOHs before stimulation with Ca2+/A23187 did not affect the time-course of exocytosis, whereas treatment with Ca2+/A23187 and exogenous DAGs (dioctanoylglycerol, oleoyl-acetyl-glycerol, or dioleoylglycerol) resulted in a dose-dependent stimulation of acrosomal exocytosis. Our results suggest that DAG, rather than PtdOH, is the important metabolite generated upon PPI hydrolysis; however, since spermatozoa lack protein kinase C, the target of DAG in most cells, a role for DAG in acrosomal exocytosis is as yet unclear.
authors.affiliation: Department of Molecular Embryology, AFRC Institute of Animal Physiology and Genetics Research, Barbraham, Cambridge, U.K.
authors.forename: E R
authors.initials: ER
authors.lastname: Roldan
authors.forename: R A
authors.initials: RA
authors.lastname: Harrison
mesh_terms: D000177:Acrosome / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology*; D005089:Exocytosis / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D010710:Phosphates / Q000378:metabolism; D010712:Phosphatidic Acids / Q000302:isolation & purification / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D011744:Pyrimidinones / Q000494:pharmacology; D012756:Sheep; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D004075:Diglycerides; D010710:Phosphates; D010712:Phosphatidic Acids; D010716:Phosphatidylinositols; D011744:Pyrimidinones; D013844:Thiazoles; D000001:Calcimycin; C047505:R 59022; D002118:Calcium