نبذة مختصرة : Objectif: Nous avons émis l'hypothèse que les glucocorticoïdes peuvent augmenter la radiosensibilité tumorale en augmentant l'oxygénation tumorale (p O 2) par inhibition de la respiration mitochondriale.Experimental Design: The effect of three glucocorticoids (hydrocortisone, dexamethasone, and prednisolone) on p O 2 was studied in murine TLT liver tumors and FSaII fibrosarcomas. Experimental Design: L'effet de trois glucocorticoïdes (hydrocortisone, la dexaméthasone, et prednisolone) sur p O 2 a été étudiée dans les tumeurs du foie de souris TLT et des fibrosarcomes FSaII. At the time of maximum p O 2 ( t max , 30 min after administration), perfusion, oxygen consumption, and radiation sensitivity were studied. Au moment de la p maximale (t max O 2, 30 min après l'administration), la consommation d'oxygène, perfusion, la sensibilité aux rayons et ont été étudiées. Local p O 2 measurements were done using electron paramagnetic resonance. Local p O 2 mesures ont été effectuées en utilisant la résonance paramagnétique électronique. The oxygen consumption rate of tumor cells after in vivo glucocorticoid administration was measured using high-frequency electron paramagnetic resonance. Le taux de consommation d'oxygène des cellules tumorales dans l'administration après glucocorticoïdes in vivo a été mesurée à l'aide d'électrons de haute fréquence de résonance paramagnétique. Tumor perfusion and permeability measurements were assessed by dynamic contrast-enhanced magnetic resonance imaging. perfusion tumorale et les mesures de perméabilité ont été évalués par la dynamique renforcée imagerie par résonance magnétique en contraste.Results: All glucocorticoids tested caused a rapid increase in p O 2 . Résultats: Tous les glucocorticoïdes testé a provoqué une augmentation rapide de la p O 2. At t max , tumor perfusion decreased, indicating that the increase in p O 2 was not caused by an increase in oxygen supply. A t max, perfusion tumorale a diminué, ce qui indique que l'augmentation de p O 2 n'a pas été causé par une augmentation de l'apport d'oxygène. Also at t max , global oxygen consumption decreased. Toujours à t max, la consommation d'oxygène global a diminué. When irradiation (25 Gy) was applied at t max , the tumor radiosensitivity was enhanced (regrowth delay increased by a factor of 1.7). Lorsque l'irradiation (25 Gy) a été appliqué à t max, la radiosensibilité tumorale a été renforcée (délai repousse augmenté par un facteur de 1,7).Conclusion: These results show the potential usefulness of the administration of glucocorticoids before irradiation. Conclusion: Ces résultats montrent l'utilité potentielle de l'administration de glucocorticoïdes avant irradiation.
Purpose: We hypothesized that glucocorticoids may enhance tumor radiosensitivity by increasing tumor oxygenation (pO2) through inhibition of mitochondrial respiration.Experimental Design: The effect of three glucocorticoids (hydrocortisone, dexamethasone, and prednisolone) on pO2 was studied in murine TLT liver tumors and FSaII fibrosarcomas. At the time of maximum pO2 (tmax, 30 min after administration), perfusion, oxygen consumption, and radiation sensitivity were studied. Local pO2 measurements were done using electron paramagnetic resonance. The oxygen consumption rate of tumor cells after in vivo glucocorticoid administration was measured using high-frequency electron paramagnetic resonance. Tumor perfusion and permeability measurements were assessed by dynamic contrast-enhanced magnetic resonance imaging.Results: All glucocorticoids tested caused a rapid increase in pO2. At tmax, tumor perfusion decreased, indicating that the increase in pO2 was not caused by an increase in oxygen supply. Also at tmax, global oxygen consumption decreased. When irradiation (25 Gy) was applied at tmax, the tumor radiosensitivity was enhanced (regrowth delay increased by a factor of 1.7).Conclusion: These results show the potential usefulness of the administration of glucocorticoids before irradiation.
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