Manipulation of experimental rat and rabbit liver tumor blood flow with angiotensin II

The effects of angiotensin II on the distribution of blood flow to experimental hepatic tumors in ten rats and rabbits were examined using blood flow tracer microspheres. The ratio of arterially introduced microspheres lodging in tumor tissue compared to the surrounding normal hepatic parenchyma was measured before and after i.v. infusion of angiotensin II-inducing incremental systemic responses. A significant elevation (P less than 0.05) in this ratio was described for both rats (3.0-fold) and rabbits (3.2-fold) following the drug infusion. Ratio elevation occurred in 37 of 40 tumors examined despite the lack of a clear dose-response relationship. In addition, angiotensin II was found to significantly (P less than 0.05) increase the number of microspheres gaining arterial access to the central portions of the tumors. In terms of internal radiation therapy, these results would indicate a substantially enhanced radiation dose reaching tumor tissue after angiotensin II infusion, while relatively sparing the surrounding normal tissue.