FLOW CYTOMETRIC ANALYSIS ON CYTOTOXIC ACTION OF AMYLOID-BETA PROTEIN FRAGMENT-25-35 ON BRAIN NEURONS DISSOCIATED FROM THE RATS

Effects of amyloid beta protein fragment 25-35, A beta P(25-35), on membrane permeability and cell viability were examined in the brain neurons dissociated from the rats using a flow cytometer and two fluorescent dyes, fluo-3 to monitor intracellular Ca2+ concentration ([Ca2+](i)) of neurons and ethidium which is impermeant to membranes of intact neurons to stain dead and dying neurons. A beta P(25-35) augmented fluo-3 fluorescence of some neurons at concentrations greater than 1 mu M, indicating an increase in [Ca2+](i) although other neurons (about 80% of total neurons) did not respond to A beta P(25-35) even at 10 mu M. A Beta P(25-35) at 1 mu M or greater increased dose-dependently the number of ethidium-stained neurons, suggesting a dose-dependent increase in number of dead and dying neurons. Results suggest that A beta P(25-35) increases the membrane permeability of brain neurons, resulting in a destabilized intracellular homeostasis that leads to neuonal death.