Vascular volume and permeability of human and murine tumors grown in athymic mice

99mTc-labeled red blood cells have been used to measure tumor vascular volume (VV). When combined with the use of 125I-labeled bovine serum albumin [( 125I]BSA) and 131I-labeled IgGs this method also provides the rapid simultaneous determination of tumor vascular permeability (VP). Using this technique the VV and VP of a human (Clouser) and a murine tumor (SL2) grown in athymic mice were determined. The relative VV were Clouser = SL2 greater than or equal to skin greater than muscle. The relative VP of BSA and IgG were Clouser greater than SL2 = skin greater than muscle. These results may explain the differences observed in the accumulation of monoclonal antibodies in human and murine tumors grown in the athymic mouse.