Lack of protection by oestrogen from radiation-induced testicular damage in the rat.

The influence of pretreatment with oestradiol dipropionate (E) on the response of the rat testis to radiation has been studied. Treatment of rats for 3 weeks with E (100 mg/kg per week) induced severe atrophy of the testis. At this time, the testes were locally irradiated to doses of 0, 4 or 15 Gy, E treatment was continued for a further week and the rats were killed 24 or 36 weeks later. Radiation alone had a marked effect on spermatogenesis as assessed by testicular weight and counts of regenerating tubule cross-sections. At 24 weeks, 8% of cross-sections were found to possess spermatogenic cells after 4 Gy and this had increased to 15% at 36 weeks. No significant regeneration was observed after 15 Gy. Similar results were obtained in those rats pretreated with E. Following irradiation alone, decreases in interstitial cell numbers and testicular luteinizing hormone (LH) receptors reflected Leydig cell damage. Again, pretreatment with oestrogen did not appear to reduce Leydig cell damage. The results of the present study suggest that pretreatment with oestrogen is not able to reduce the testicular damage induced by moderate to high single doses of radiation.