Morphologic and functional correlates of plasma membrane injury during oxidant exposure

Plasma membrane injury by exposure to hydrege peroxide was examine in a renal epithelial cell line (LLC-PK1). Morphologic and functional parameters of plasma membrane integrity were studied in an attempt to eludicate the sequence of membrane alterations during the evolution of hydrogen peroxide-mediated injury. These parameters included plasma membrane potential and permeability, plasma membrane bleb formation, cellular size, and plating efficiency. Plasma membrane potential was the earliest parameter affected by hydrogen peroxide exposure. Half maximal depolarization occured within 15-30 min of exposure to 1 mM, after 10-15 min exposure to 100 mM and after over 150 min exposure to 10 μM hydrogen peroxide. After exposure to 1 mM hydrogen peroxide, the following sequence of events was seen; increased plasma membrane blebbing (30 min), cell swelling (90-125 min) and increased plasma membrane permeability (150-240 min). After a 30 min exposure to 1 mM hydrogen peroxide, cellular plating afficiency, measured at 24 h, was reduced by 50% (P < .001). These changes were accelerated, although their order of apperance was unchanged, at higher concentrations of hydrogens peroxide. We conclude that functional and morphologic expressions of cellular imjury in this model occur in a defined sequence with plasma membrane depolarization representing the earliest marker of membrane injury during hydrogen peroxide exposure.