Discussion

Anti-immunoglobulin (0.13 mM) stimulation of WEHI-231 cells resulted in a unique pattern of increasing and decreasing levels of glycerophospholipids. A wide variety of phosphatidylinositols, phosphatidylglycerols, and phosphatidylcholines decreased in concentration during the 6- and 15-minute time points, with corresponding increases in lysophospholipid levels. By the fourth hour, the GPL levels had essentially returned to their prestimulated states.

Due to detection limitations using triple quadrupole MS, diacylglycerols (DAGs) were not routinely analyzed in this study. Under our current experimental conditions, it is not possible to scan for DAGs and the remaining lipid classes simultaneously. In the future, samples will be split and changes in DAG levels will be monitored using an alternative procedure. Preliminary analysis measuring polyphosphoinositide levels is already underway and will be described in a subsequent report. The current methodology appears to be effective but cannot be run in parallel with other phospholipids. Detection of these species will almost certainly require multiple extractions and or separation by HPLC.

Mapping comprehensive lipid changes in time is thought to have many positive applications in cellular biology and cellular signaling. It is believed that data of this type will prove useful in hierarchical clustering schemes as another method in differentiating receptor-mediated cellular events involving lipid second messengers as well as membrane compositional remodeling. It is further believed that these arrays form a fingerprint that can be used to identify specific cellular responses and as such may prove useful in diagnostic profiling and elucidating lipid product-substrate relationships.