Author/Editor		Koritnik, Katarina; Coer, Andrej
Title		The role of thyroid radiation carcinogenesis in rats
Translated title		Vloga tiroksina pri karcinogenezi ščitnice
Type		članek
Source		Radiol Oncol
Vol. and No.		Letnik 32, št. 4
Publication year		1998
Volume		str. 393-9
Language		eng
Abstract		The aim of this study was to test the hypothesis on the protective role of thyroxin administration before and during irradiation on the occurrence of thyroid carcinoma in rats. Application of thyroxin before and during irradiation was expected to decrease production of thyrotropin by the hypophyseal feedback mechanism, caused by radiation damage of thyroid tissue. Stabilizing the thyroid cells in this way during irradiation would thus make them less radiosensitive. In the experiment, we first divided 81 three to four week old Wistar strain rats of both sexes into two groups, i.e. thyroxin (T4) and water (H2O). The T4 rats were injected 1% thyroxin solution (0.01 mg/100 g body weight) twice a day for 15 days, while the H2O rats received saline in the same way. After ten days, the two main groups were divided each into two subgroups. The rats from both irradiated subgroups (T4/X and (H2O/X) recieved 10 Gy to the neck area. They were iradiated with a telecobalt machine for five consecutive days with one direct field. During a two years follow - up, all moribund animals were sacrificed and their thyroid glands taken. The rest of the thyroid glands were taken at the end of the experiment. All glands were pathohistologically analysed. Besides, all suspicious and enlarged extrathyroid organs and tissues were examined and the occurrence of tumors was noted. Pathohistological examination revealed the occurrence of 8 thyroid carcinomas and 7 adenomas in the H2O/X group, and 3 adenomas in the T4/X group. In the iradiated group of rats without thyroxin, significantly (P = 0.01) more thyroid carcinomas occurred than in the irradiated group without thyroxin.
Summary		Namen študije je bil preveriti hipotezo o zaščitni vlogi dajanja tiroksina podganam pred obsevanjem in po njem, na pojavljanje ščitničnega karcinoma. Dajanje tiroksina pred in med obsevanjem naj bi preko povratne zveze s hipofizo preprečilo povečano izločanje tirotropina, povročeno z radiacijsko okvaro ščitničnega tkiva. Na takšen način stabilizirane celice naj bi bile med obsevanjem manj radiosenzibilne. V poskusu smo 81 podgan seva Wistar obeh spolov, starih 3 do 4 tedne najprej razdelili v dve skupini, v tiroksinsko (T4) in vodno (H2O). Tiroksinski skupini smo 15 dni dvakrat dnevno intraperitonealno injicirali enoodstotno raztopino tiroksina (0.01 mg/100 g telesne teže), vodna skupina pa je na enak način dobivala sterilno fiziološko raztopino. Po 10 dneh smo vsako od osnovnih skupin razdelili v dve podskupini; podgane iz obeh obsevanih podskupin (T4/X in H2O/X) so prejele 10 Gy na področje vratu. Na telekobaltovem aparatu smo jih 5 dni zapored obsevali z direktnim poljem. Med dveletnim opazovanjem smo sproti žertvovali vse živali v slabem stanju in jim odvzeli ščitnice. Preostale ščitnice smo odvzeli ob koncu poskusa. Vse žleze smo patohistološko analizirali. Poleg tega smo pregledali vse sumljive in povečane ekstratiroidne organe in tkiva ter zabeležili vsa pojavljanja tumorjev. Ugotovili smo, da se je v skupini H2O/X pojavilo 8 ščitničnih karcinomov in 7 adenomov, v skupini T4/X pa trije ščitnični adenomi. V skupini obsevanih podgan brez tiroksina je bila incidenca karcinomov ščitnice statistično signifikantno (P = 0,01) večja kot v obsevani skupini s tiroksinom. Z opisanim poskusom je bila potrjena hipoteza o zaščitni vlogi dajanja tiroksina pred in med obsevanjem pri postiradiacijski ščitnični karcinogenezi pri podganah.
Descriptors		NEOPLASMS, RADIATION-INDUCED THYROID NEOPLASMS THYROXINE RATS, WISTAR