Capillary blood flow in the amelanotic melanoma of the hamster after isovolemic hemodilution 1

Abstract

In malignant tumors, spontaneous arteriolar vasomotion disappeared already during earliest tumor growth (tumor weight less than 200 mg) suggesting that arterioles supplying a malignant tumor with blood are maximally dilated from the very beginning of tumor growth. As a result, the viscosity of blood becomes a limiting factor of tissue perfusion. To evaluate the effects of isovolemic hemodilution in a malignant tumor, a transparent chamber model was used in conjunction with a subcutaneously growing amelanotic melanoma of the hamster. Quantitative intravital microscopy (video image analysis) and a platinum multiwire electrode were utilized to study the tumor microcirculation. Isovolemic hemodilution was performed by exchange of blood vs. Dextran 60 to lower the systemic hematocrit to 30% in 21 animals. Capillary flow increased significantly and improved tissue pO₂ on the tumor’s surface without any change in capillary density. Since tumor growth was accelerated after hemodilution, these data suggest to combine with hemodilution other treatment modalities to improve blood-mediated tumor therapy.