Increase in tumor vascular area due to increased blood flow by angiotensin II in rats.

For further elucidation of the microhemodynamics in tumor tissue, the "vascular level," percentage of the vascular area to tissue area, was measured in DONRYU rats. Changes in the vascular level due to angiotensin II were analyzed by a point-counting method in normal and tumor tissues within a rat transparent chamber. The vascular level in normal subcutis changed from 21.8 to 18.6% when the mean arterial pressure was elevated from 102.3 to 155.9 mmHg. The coefficient of change due to angiotensin II was 0.85. The vascular level in tumor tissue was distributed inhomogeneously from 0 to 48.5% with an average of 19.7%. It increased to 33.9% (range: 8.7-57.6%) with an elevation of the mean arterial blood pressure from 103.5 to 150.8 mmHg. The coefficient of change due to angiotensin II was 2.08 in tumor tissue. Moreover, the tumor vascular level increased at a higher rate in the areas with a lower vascular level.