Stage-specific expression of Gadd45 induced by X-irradiation in rat spermatogenesis

Purpose: Gadd45 is involved in the response to DNA damage in somatic cells. The effect of X-irradiation and chemical treatments on expression of Gadd4 5 and two other 53-regulated genes, p21 and cyclin-G, was studied in rat te stis. Materials and methods: The reverse-transcriptase polymerase chain reaction (RT-PCR) was performed on testis extracts of control, X-irradiated (6 Gy), etoposide (10 mg kg(-1)) and adriamycin (5 mg kg(-1))-treated rats. For sta ge-specific analysis, seminiferous tubules were isolated and segments repre senting the 14 epithelial stages were obtained. Results: In whole testis extracts, increases in Gadd45, p21 and cyclin-G ex pression were detectable after irradiation, but not after etoposide or adri amycin treatments. Analysis of fractions consisting of defined epithelial s tages showed a high expression of Gadd45 in stages VII-XII and of p21 in st ages VII-VIII. Irradiation significantly increased the level of Gadd45 mRNA in stages VI-VIII and of p21 mRNA in stages VI-I. Although no overall incr ease could be observed in whole testis samples of the etoposide-treated rat , stage-specific analysis revealed an induction of p21 expression in stages XIII-I. Gadd45 and cyclin-G mRNA were localized to spermatocytes and round spermatids known to express p21. Conclusions : Although X-irradiation, etoposide and adriamycin are known sp ermatogenic mutagens and activators of apoptosis, only X-rays induce slight ly Gadd45 expression in testis. This small induction was very stage specifi c.