Microvessel density and endothelial cell proliferation after amifostine (Ethyol (R)) administration in vivo

Background: As amifostine is rapidly metabolised by the membrane-bound and capillary alkaline phosphatase to the active metabolite WR-1065, microvesse l density in normal and cancer tissue may influence the therapeutic potenti al of the pro-drug WR-2721. Thus, it is of interest how the administration of amifostine itself alters vascular density. Materials and Method: For thi s study fertilized eggs were used and 0.05 ml amifostine (25.7 mu g) was in jected into the area vasculosa. As controls untreated area vasculosa were e xamined as well as eggs treated with 0.05 ml NaCl 0.9%. 48 hr after injecti on the vascular density was determined by histometrical methods. Applying t he LAB method we performed immunohistochemical analysis of the proliferatin g cell nuclear antigen of endothelial cells. Results: There was a significa nt (p<0.001) difference in vascular density with a mean microvessel count o f 25.08 (+/- 8.45 SD) vascular intersections/mm(2) in the untreated control , 30.40 (+/- 12.84 SD) in the NaCl control and 53.69 (+/- 24.56 SD) in the amifostine treated area. There was also a significant (p<0.001) difference in endothelial cell proliferation (PCNA) between untreated controls with a mean PCNA positivity of 14.05 (+/- 5.28 SD) and amifostine treated area vas culosa with a mean PCNA positivity of 32.22 (+/- 18.14 SD). Conclusion: A s ingle dose administration of 25.7 mu g amifostine induces endothelial cell proliferation and subsequent neovascularisation in the area vasculosa of th fertilised egg.