Effect of Midkine (MK) on Cultured Spinal Motor Neurons Damaged by Oxidative Stress

To evaluate the effect of midkine (MK), neurotrophic factor on cultured mouse spinal motor neuron, NSC-19 which was inhibited by glucose oxidase (GO)-induced oxygen radicals, MTT assay and neurofilament enzymeimmunoassay were carried out after NSC-19 cells were preincubated with various concentrations of midkine for 2 hours prior to exposure of glucose oxidase. The results were as follows : 1. MK increased the rate of cell viability and neurofilamental development in a dose-dependent manner on motoneurons inhibited by glucose oxidase-induced oxygen radicals. 2. MTT₅₀ value was 25 mU/ml GO. 3. GO-induced oxygen radicals were toxic on cultured motor neurons in a time and dose-dependent manner. 4. GO-induced oxygen radicals induced the decrease of cells in number and the loss of neurites in cultured mouse spinal motor neurons. From above the results, it is concluded that oxygen radicals are toxic in cultured mouse spinal motor neurons, and selective neurotrophic factors such as MK enhance the viability of motor neurons inhibited by oxygen radicals.