Shedding of tumor cell surface membranes

Abstract

Mastocytoma P815 cells are induced to form and shed membrane vesicles (MV) from their surfaces by incubation at low temperature (4 degrees C) for 1 hr. and subsequently allowing them to warm up to room temperature (22 degrees C). Within 1-2 hrs. at room temperature, up to 90% of the P815 cells form and shed MV from their surfaces. Both cells and vesicles remain trypan blue-excluding during the MV shedding process. This process is energy dependent in that it can be inhibited by 2-deoxyglucose, sodium azide and 2-4-dinitrophenol. The shed MV can be harvested by centrifugation on a 6% Ficoll cushion and quantitated in terms of protein content. The shedding of membrane vesicles from the tumor cell surfaces results in a significant reduction in the cell size.