Cell membrane changes induced by the cytolytic peptie, melittin, are detectable by 90 degree laser scatter
The 90" light scatter parameter of the flow cytometer was used to observe changes in the membrane of human lymphoblastoid cells (HMy2) as a result of the action of the cytolytic peptide, melittin. There was a rapid and concentrationdependent increase in 90" light scatter after incubation of the cells with melittin, with the level of 90" light scatter reaching a maximum after 2 min. Even after all the cells were killed, as determined by ethidium bromide incorporation, the 90" light scatter continued to increase. Further, the 90" light scatter changes were temper- memature dependent. The data are consistent with the formation of lipid vesicles, either attached to the cell membrane or intracellular, as confirmed by electron microscopy of cells treated with melittin. The results demonstrate the use of the flow cytometer to detect changes in the integrity of the cell membrane.