Microcirculatory blood flow, capillary morphology and local oxygen pressure of the hamster amelanotic melanoma A-Mel-3.

Transparent chambers and permanent indwelling catheters were implanted in the dorsal skin flaps of 24 inbred golden Syrian hamsters. After 48 hours, 4 x 10(4) amelanotic melanoma cells (A-Mel-3) were transplanted sc (12 hamsters) in areas exposed for intravital microscopy. A platinum multiwire electrode and techniques for a quantitative analysis of television images were used for measurements of local oxygen pressure (PO2), capillary blood cell velocity, capillary density, and capillary diameter and length, whereas capillary morphology was evaluated by electron microscopy. Compared to the mean local PO2 of the skin flaps of controls (12 hamsters), the mean local PO2 on the tumor surface of melanoma-bearing hamsters decreased with tumor size. Although capillary density of the melanoma was elevated 4 days after tumor transplantation, it decreased significantly until day 12. Of hemodynamic significance were huge platelet conglomerates in short, dilated capillaries. Electron microscopy revealed endothelial hyperplasia, open endothelial junctions, and disintegration of the capillary endothelium. These findings strongly suggest that elevated microvascular resistance, intratumor tissue pressure, and widening of intercapillary distances in the melanoma might significantly diminish the impact of chemotherapeutic treatment.