Submitted on March 27, 2008
Revised on June 23, 2008
Accepted on June 23, 2008
Lipid levels in sperm, eggs, and during fertilization in Xenopus laevis
Douglas W. Petcoff, William L. Holland, and Bradley J. Stith
Biology, University of Colorado Denver, Denver, CO 80217
Corresponding Author: brad.stith{at}ucdenver.edu
Critical developmental periods, such as fertilization, involve metabolic activation, membrane fusion events such as sperm-egg, or plasma membrane-cortical granule merger and production and hydrolysis of phospholipids. However, there has been no large-scale quantification of phospholipid changes during fertilization. Using an enzymatic assay, traditional fatty acid analysis by TLC and gas chromatography along with a new method of phospholipid measurement involving HPLC separation and evaporative light scattering detection, we report lipid levels in eggs, sperm, and during fertilization in Xenopus laevis. Sperm were found to contain different amounts of phospholipids as compared to eggs. During fertilization, total phosphatidylinositol, lysophosphatidylcholine, sphingomyelin and phosphatidylserine decreased, ceramide increased whereas there was no change in phosphatidylcholine, cardiolipin or phosphatidylethanolamine. Fatty acid analysis of phospholipids found numerous changes during fertilization. As there is an increase in sn 1,2-diacylglycerol at fertilization, the fatty acids associated with this increase and the source of the increase in this neutral lipid were examined. Finally, activation of phospholipase C, phospholipase D, phospholipase A2, autotaxin and sphingomyelinase at fertilization is discussed.
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