ObjectiveTo observe the effects of angiostatin on the activity of extra-cellular signal-regulated protein kinase (ERK) of retinal microvascular endothelial cells of mice.MethodsAngiostatin was separated and purified by l-lysine sepharose 4B from human plasma. The primary retinal microvascular endothelial cells were divided into 4 groups: the control group, vascular endothelial growth factor (VEGF) 10 ng/ml group, angiostatin 130 μg/ml group, and VEGF (10 ng/ml) + angiostatin (130 μg/ml) group. The expression of ERK1 was assayed by Westernblotting method 1, 2, 5, 10, 15, and 30 minutes after the treatment of angiostatin.ResultsCompared with the control group, the expression of ERK-1 reduced 1 minute after treatment, reduced markedly after 10 minutes. After 30 minutes, no differences of the expression of ERK were seen between the control group and angiostatin group. The activation of ERK-1 of retinal microvascular endothelial cells occurred after stimulated by VEGF, and at the pitch at the peak after 5 minutes. The level of ERK in VEGF group increased 210% than that in the control (P＜0.05). After 30 minutes, no significant difference of the level of ERK between VEGF and the control group. And because of angiostatin, the expression of ERK-1 decreased 11.9%(1 minute)、17.9%(2 minutes)、38.7%(5 minutes)、49.3%(10 minutes) （P＜0.05）、27.9%(15 minutes)、1.12%(30 minutes) respectively.ConclusionsAngiostatin can effectively block the signal path through which VEGF transmits from outside of the cell to cellular nuclei. (Chin J Ocul Fundus Dis, 2005,21:170-173)