The Selective Protection of Normal Tissues by Irradiation of Tumor-Bearing Mice in Hypoxic Hypoxia

Modulation of Radioprotective Effects of Respiratory Hypoxia by Changing the Duration of Hypoxia before Irradiation and by Combining Hypoxia and Administration of Hemopoiesis-Stimulating Agents

“…The time of exposure to this lethal radiation dose was 15 minutes. Inhalation of the hypoxic gas began at various time intervals (5,10,20,30,40, 50 and 60 minutes) before the start of irradiation and continued during irradiation. After irradiation the mice were returned to the normooxic (21% O 2 ) conditions.…”

“…When a high dose rate of irradiation was used (6.5-9.0 Gy/min), the radioprotective effect of hypoxia in mice was diminished with prolongation of its action from 1-2 to 20-40 minutes before irradiation even when low levels of 6.0-6.5% O 2 was used [28,30]. Again, pO 2 in the subcutaneous tissue did not change after its initial drop at the beginning of hypoxic gas inhalation.…”

Preoperative Hypoxyradiotherapy of Colorectal Carcinoma

“…Specifically, the effect of hypoxia-induced radioprotection is highest during the first few minutes of hypoxia and decreases thereafter as a consequence of the adaptive changes in cell metabolism caused by hypoxia [30,32,33].…”

“…Theoretical assumptions of differential radioprotection by acute hypoxia to tumor and normal tissues have been verified experimentally [17,22,33,39] as well as clinically [1,23,24,[25][26][27][28]. Thus, induction of acute hypoxia has been introduced as a safe procedure allowing administration of radiation doses greater than the tolerance limits of normoxic tissues.…”

Hypoxic Versus Normoxic External-Beam Irradiation of Cervical Carcinoma Combined with Californium-252 Neutron Brachytherapy

“…Specifically, hypoxia-induced radioprotection is most effective during the first several minutes of hypoxia and decreases thereafter. This diminishing protective effect is a consequence of the adaptive changes in cell metabolism caused by the hypoxia [46,51,52].…”