A transparent chamber was implanted in the dorsal skin flap of 32 Syrian
gold hamsters, 48 h after microsurgery, 4x10(4) cells of the
amelanotic melanoma A-Mel-3 were transplanted s.c. in the area exposed for daily in vivo microscopy (16 animals). A
platinum multiwire
electrode and quantitative video-techniques were utilized for measurements of local pO2, microvascular morphology and measurements of local PO2, microvascular morphology and capillary hemodynamics. When compared to controls (16 animals), mean local PO2 on the
tumor's surface decreased with
tumor development. The density of erythrocyte perfused capillaries in the
melanoma was elevated 4 days after humor
transplantation indicating excessive neovascularization. Probably due to increased intratumor tissue pressure and
thrombosis, capillary density decreased significantly until day 12, whereas mean capillary blood cell velocity did not change. Of microhemodynamic significance were huge platelet conglomerates consistently noted in short, dilated capillaries as the
melanoma edge. As a result, the capillary filling time (15.7 s for
melanoma capillaries, 3.2 s for control preparations) was prolonged suggesting an increase in capillary resistance. These findings might indicate that the efficacy of
melanoma treatment is diminished by an enhanced capillary resistance. Intratumor tissue pressure and
thrombosis with concomitant widening of intercapillary distances might significantly affect the
therapy of
melanomas.