[Enhancement of vascular level in tumors under angiotensin-induced hypertension]

The change in tumor vascular area seems to be one of the important factors influencing drug delivery to tumor tissue. By means of a point-counting method we analyzed changes in the "vascular level", percentage of the vascular area to tissue area, in two tumors; AH272, AH109A, comparatively under angiotensin-induced hypertension. In tumor AH272, the vascular level changed from 27.4% (range; 19.7-34.9%) to 38.5% (range; 28.2-48.1%) when mean arterial blood pressure elevated from 98.3 to 151.7 mmHg. The change coefficient due to angiotensin II was 1.42. The vascular level in AH109A tumor tissue increased from 19.7% (range; 0-48.5%) to 33.9% (range; 8.7-57.6%) with an elevation of mean arterial pressure from 103.5 to 150.8 mmHg. The change coefficient was AH109A in 2.08. In-homogeneity in the vascular level in tumor tissue was more marked in AH109A than in AH272. Moreover, it was revealed in AH 109A that the increase in the vascular level due to angiotensin II was greater in the areas with a lower vascular level. This seems to be caused by the phenomenon that blood flow appearing under angiotensin-induced hypertension in tumor vessels that lacked blood flow at normotension. In conclusion, selective increase in vascular level was seen in both tumors under angiotensin-induced hypertension.