Tumor Vessel Innervation and Influence of Vasoactive Drugs on Tumor Blood Flow

An influence of vasoactive drugs on tumor blood flow might be dependent upon the incorporation of normal contractile vessels in the growing tumor mass and upon the degree of connection between tumor vessels and normal vessels in the transplantation area. The adrenergic innervation of the vessels in tumors transplanted i.m. or into the anterior chamber of the eye was studied by a histochemical technique for visualization of catecholamines. Systematically administered vasoactive drugs can indirectly modify the tumor blood flow by affecting the systemic blood pressure. However, as the arteriolar supply to the tumor is based on normal vessels, one might expect vasoactive drugs to modify the tumor blood flow in the same way as in normal tissues. In experimental mammary tumors, blood vessels showed a progressive loss of ability to respond to vasoactive drugs as the tumor enlarged. The blood-flow rate of tumors seems to be very sensitive to changes in systemic blood pressure which might be induced by anesthesia.