In the presence of inorganic orthophosphate, the platelet-derived endothelial growth factor (PD-ECGF) thymidine phosphorylase (TP) (gliostatin) catalyses the reversible phospholytic cleavage of thymidine and deoxyuridine to their corresponding bases and 2-deoxyribose-1-phosphate. It is both chemotactic