Fig. 6.

l-Arginine blocks the CSE-induced apoptosis in endothelial cells. HAECs were incubated with 200 μM of l-arginine (columns 3 and 4), or 400 μM of l-NAME (columns 5 and 6) for 30 min followed by 0.02 U CSE exposure for 4 h (columns 2, 4 and 6). l-Arginine or l-NAME pretreatment altered CSE-induced endothelial apoptosis (a) and caspase-3 activity (b). Data are presented as means + S.E.M. (N = 3) at each treatment condition. There was a significant among group difference by ANOVA test (P < 0.01). CSE treatment increased cell death significantly (P < 0.001 comparing to controls). However, l-arginine pretreatment reduced the cell death to the level not different from the control cells (P = NS). Yet, l-arginine treatment alone did not alter the rate of cell death. Although l-NAME treatment alone also did not change the cell death, l-NAME pre-conditioning followed by CSE treatment significantly increased the percentage of cell death comparing to CSE treatment alone (P < 0.05). Changes in caspase-3 activity were similar to the percentage of cell death except that the caspase-3 activity did not return to the control level in cells preconditioned with l-arginine and treated with CSE. *The post hoc Bonferroni correction was applied to the P values for between group comparisons.