Figure 2.

VEGF triggers MMP2 secretion by canary forebrain endothelial cells. A, Both pro-MMP2 and pro-MMP9 gelatinase activities were noted by gel zymography of adult female HVC tissue extracts, taken from birds given testosterone and killed 8 d after testosterone treatment. These gels were developed briefly, highlighting the gelatinase activities associated with the MMP2 and MMP9 pro- forms, which are both more abundant than their active products, and enzymatically active in denaturing gels like these. B, Media from 2 d serum-free cultures of isolated canary forebrain endothelial cells were analyzed by gel zymogram; 4 μg of sample were loaded per well. VEGF exposure induced a significant increment in gelatinase activity; testosterone treatment did not. C, D, Pixel analyses of gel zymograms for active and pro-MMP2. Pixel intensity from different gels was normalized against a common control. E, RT-PCR showed that CBECs exhibited increased MMP2 transcript levels in response to VEGF. MMP9 mRNA was also expressed, but exhibited no evident response to VEGF or testosterone. **p < 0.01 by ANOVA with Bonferroni t tests.