Blood flow in irradiated mouse sarcoma as determined by the clearance of xenon-133.

Abstract

133Xe dissolved in 0.9% NaCl solution was injected directly into KHT sarcomas in C3H mice in order to study tumor blood flow. The rate of blood flow in ml/100 g/min was calculated from the clearance half-time and the partition coefficient. The mean rate of blood flow in the tumors of unanesthetized control mice was 21.2 ± 0.8 ml/100 g/min, which was significantly faster than the blood flow in the tumors of pentobarbital-anesthetized control mice. 133Xe was cleared exponentially in virtually all tumors, and rate of clearance decreased with increasing tumor volume in tumors larger than approximately 500 to 600 cu mm; in smaller tumors there was no conclusive evidence of dependence of clearance rate on size. Clearance rate was unaffected by multiple daily injections of 133Xe. At 3 hr after localized tumor irradiation (250 kV; half-value layer, 5.9 mm Al) with doses greater than 1,000 rads, blood flow tended to decrease with increasing radiation dose. At 3 to 4 days postirradiation, rate of blood flow was significantly increased in tumors receiving 1,000 rads; blood flow was also increased in tumors exposed to 2,000 and 4,000 rads, but not until approximately 7 days. Rate of blood flow decreased at 3 hr and 3 to 4 days in tumors irradiated with 8,000 to 16,000 rads. The postirradiation increases in blood flow were not correlated simply with gross tumor shrinkage, although tumor growth was slowed proportionally to radiation dose. Thus, irradiation brought about changes in rate of blood flow in the KHT sarcoma, and these changes were dependent on both radiation dose and postirradiation time. The observed time course of radiation-induced blood flow changes may partially account for the tumor reoxygenation shown in our previous studies and those of others.

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