APOPTOSIS DEPENDENT DECREASE OF THE INTRAMEMBRANE ION TRAFFIC IN CULTURED MOUSE FIBROBLASTS SHOWN BY CONDUCTIVITY DISPERSION

We have investigated the intramembranal ion traffic in apoptotic 3T6 c ells in culture. Apoptosis was induced by various treatments, such as serum deprivation, high density growth and hydrogen peroxide at subnec rotic doses. Cell death was assessed by nucleosomal DNA fragmentation, single cell electrophoresis, immunofluorescence and histological stai ning. To study the modifications of membrane structure and function, w e adopted a well established biophysical strategy based on the measure ment of the electrical conductivity of cell suspensions, as a function of the frequency of the electrical field applied to the sample. A com parison between the conductivity of normal and apoptotic cell suspensi ons shows that programmed cell death causes a decrease of membrane con ductivity which indicates a diminished intramembranal ion traffic. Our results strongly suggest that one of the early events in the triggeri ng of apoptosis is represented by an overall reduction of plasma membr ane function. Finally, our results are in agreement with the idea that the nucleus is not the sole target of the apoptotic process.