Retina contains endogenous heparinase activity

Abstract Heparin binding growth factors (HBGF), a major component of retinal endothelial cell growth factor activity, have been located particularly to a storage site in the vascular basement membrane, where they are bound to heparan sulphate in a relatively inactive state. It has been suggested that angiogenic activity in the retina may be released, during basement membrane degradation, by heparinase enzymes. We now report that mitogenic saline extracts of retina contain heparinase-like activity, whereas non-mitogenic retinal homogenate does not. However, heparinase-like activity may only account for part of the mitogenic activity in retinal extract. In previous studies we have shown that the absence of mitogenic activity in retinal homogenate is due to a heat-labile inhibitor. Heat-treatment of retinal homogenate restored mitogenic activity to 60% of that in retinal extract, but this heat-treated homogenate still lacked heparinase activity.