Evidence that epinephrine acutely redistributes blood flow to experimental intrahepatic tumors

Tumor microcirculation was studied in Sprague-Dawley rats with solitary intrahepatic implants of Walker carcinosarcoma tumors. Thioflavine S (TS), a fluorescent dye that stains capillary endothelium acutely, was injected intraportally or intra-arterially in order to demonstrate patterns of blood flow through normal liver tissue and through tumor. The dye was given immediately after intraportal injection of 10 micrograms of epinephrine in some animals and 3 minutes after the epinephrine in others. Control animals received TS alone. Additional animals were given TS immediately after intra-arterial epinephrine. The degree of resulting fluorescence in tumor and liver was graded subjectively from 0 to 3+. In the controls and in animals receiving TS 3 minutes after epinephrine, fluorescence in the centers of tumors was absent or, at most, faintly present. In contrast, all animals given epinephrine either intraportally or intra-arterially immediately before the dye showed intense fluorescent staining within the centers of the tumors. Subjective grading averaged 0.6 +/- 0.1 in the controls, 2.2 +/- 0.1 in those receiving intraportal epinephrine immediately before TS, and 1.0 +/- 0.3 in those receiving TS 3 minutes after epinephrine. Results were significantly higher in the latter group (p less than 0.01). Subjective grading in animals receiving intra-arterial epinephrine immediately before TS averaged 2.5 +/- 0.3. These experiments confirm previous studies in this laboratory that demonstrated an acute short-lived redistribution of blood flow into the centers of intrahepatic tumors after administration of epinephrine.