Reduktion akuter radiogener Schädigungen durch Natriumselenit. Wirksamkeit unter fraktionierter Bestrahlung der Glandula parotis der Ratte

BACKGROUND: In vitro studies show that sodium selenite is a potential radioprotector in normal cell cultures, but not tumor cells. The aim of this study was to evaluate the cytoprotective potency of sodium selenite during conventional fractionated irradiation of rat salivary glands, but also on tumor response and metastasis frequency of rhabdomyosarcomas R1H.

METHOD: The head-neck area of male WAG/RijH rats and the tumor in the flank were irradiated with (60)Co-gamma-rays (60 Gy/30 fractions/6 weeks). Sodium selenite (15 microg/kg body weight) was applied through a venous port 30 min before irradiation. Rats of a control group were treated in the same manner with an equal volume of physiologic sodium chloride. In the course of treatment the salivary glands were extirpated at different stages and examined histopathologically. The evaluation of the gland function was performed prior to and after radiotherapy by sialoscintigraphy. Tumor volume was measured during irradiation and plotted in tumor-volume curves. Rat body weight was determined sequentially to estimate the general constitution of the animal during the treatment.

RESULTS: Irradiation caused dose-dependent damage in the salivary glands. Intra- and intercellular edema (16 Gy), vacuolization (30 Gy), degranulation (46 Gy), and necrosis of the acinar cells (60 Gy) occurred. Sodium selenite delayed the development of the described damage, and the amount of necrotic acinar cells after the application of 60 Gy was reduced (control: 75% vs sodium selenite 30%), confirmed by the sialoscintigraphic results. The loss in gland function in the control group was 44% vs 74% (p<0.05) in the sodium selenite group. Sodium selenite had no influence on the response of R1H tumors to radiation and general constitution.

CONCLUSIONS: Based on morphological and sialoscintigraphic findings, a cytoprotective effect on acute toxicity of rat salivary glands could be detected under irradiation with synchronous application of sodium selenite. In addition, no effects on tumor response and metastasis frequency were observed. The general animal constitution was not affected by additional medication with sodium selenite during irradiation.