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Increase in DNA single-strand break rejoining by continuous exposure of human mononuclear blood cells to radioiodine ((131)I) in vitro.

Abstract：

:Radioiodine ((131)I) induced a dose- and time-dependent increase in DNA single-strand breaks (DNA-ssb) in human (G0) mononuclear blood cells (MNC) in vitro. Incubation of MNC with 22MBq (131)I/ml at 4 degrees C caused a linear, time-dependent induction of DNA-ssb (increase in elution rate: 24.7 x 10(-3) h(-1) per 100 min incubation with (131)I). However, if MNC were incubated at 37 degrees C a decrease in the slope of the time effect curve was observed after about 300 min incubation with 22 or 30 MBq (131)I/ml. The goodness of fit of different regression models was assessed by Akaike's Information Criterion (AIC). The best fit was obtained for a non-linear model (y=a+bx+cx(0.5); AIC=53.5; where x is incubation time and y is elution rate), whereas other models including the linear regression model y=a+bx; AIC=38.6) were worse. As the total induction of DNA-ssb at 4 degrees C was constant with time, the decrease in the slope of the time effect curve (DNA-ssb versus time) at 37 degrees C can be interpreted as an increase in rejoining of DNA-ssb. Inhibition of both RNA and protein synthesis clearly increased the extent of DNA-ssb observable after incubation with (131)I. Thus, during continuous exposure of MNC to (131)I, proteins were synthesized which rejoined DNA-ssb. However, incubation of MNC with (131)I (44 MBq/ml) at 37 degrees C under conditions expected to lead to inhibition of RNA and/or protein synthesis still resulted in a decrease of the slope of the time effect curve, indicating a stimulation of DNA-ssb rejoining. Thus, we favour the hypothesis that the increase in the activity of DNA-ssb rejoining, besides de novo synthesis of repair enzymes, is also caused by a post-translational stimulation of DNA-repair enzymes and that this stimulation possibly is mediated by DNA-fragments.

journal_name

Int J Radiat Biol

journal_title

International journal of radiation biology

authors

Hengstler JG,Bockisch A,Fuchs J,Grimm W,Zapf AO,Lade K,Meinert R,Oesch-Bartlomowicz B,Tanner B,Oesch F

doi

10.1080/095530097143103

subject

Has Abstract

pub_date

1997-11-01 00:00:00

pages

607-13

issue

eissn

0955-3002

issn

1362-3095

journal_volume

pub_type

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Increase in DNA single-strand break rejoining by continuous exposure of human mononuclear blood cells to radioiodine ((131)I) in vitro.