Figure 3.

Homocysteine-mediated neuronal cell death. (a) Cultures incubated for 6 days in various concentrations of d,l-homocysteine (HC). Data are the means ± SEM of four replicate values from each of three pooled experiments. Asterisks indicate statistically different from control value (∗, P < 0.05; ∗∗, P < 0.01). (b) Neuroprotective effects of the NMDA antagonists dizocilpine (MK-801, 10 μM), memantine (12 μM), and superoxide dismutase/catalase (SOD/CAT, 50 units/ml each) from 100 μM d,l-homocysteine-mediated neurotoxicity. Cultures were incubated for 6 days in the presence of homocysteine before the assessment of neurotoxicity. Data are the means ± SEM from a representative experiment (performed with quadruplicate samples and repeated seven times). Asterisks indicate statistically different from control value and from the homocysteine groups treated with the NMDA antagonists dizocilpine or memantine (∗∗, P < 0.01). Note that although the superoxide dismutase/catalase value was not significantly different from the homocysteine group, it was also not significantly different from the control group (at either the P < 0.05 or 0.01 levels), indicating an intermediate save from homocysteine-induced neurotoxicity.