RNA metabolism, DNA damage and cellular resistance to X-rays: investigations in chick embryo and rat cells.

ABSTRACT

Three hours after X-irradiation in vivo with 8 Gy the in vitro incorporation of [3H]uridine into total RNA of liver(L)- and brain(B)-cells of the chick embryo was reduced to 77% and 90%, respectively; the mRNA fraction was strongest inhibited. Under the same conditions, protein synthesis of L-cells declined to 62%, while protein synthesis of B-cells was not influenced. RNA and protein metabolism was not altered following X-irradiation in vitro (1.75-56 Gy). Compared to thymic- and splenic cells of the rat, chicken embryo cells exhibited higher constitutive poly(adenosine diphosphate-ribose)polymerase activity and lower X-irradiation-induced DNA damage. Whereas the slight inhibition of RNA and protein synthesis by X-irradiation in ovo may be an abscopal and/or secondary phenomenon reflecting DNA and/or cellular damage, the present investigations comprising various cell types argue for an efficient DNA repair in chicken embryo cells caused, at least partly, by a high constitutive activity of DNA repair proteins.