HORMONE-TREATMENT AFTER IRRADIATION STIMULATES RECOVERY OF RAT SPERMATOGENESIS FROM SURVIVING SPERMATOGONIA

The possibility of stimulating the recovery of spermatogenesis after i rradiation using hormone treatment was tested in LBNF(1) rats. At 10 w eeks after irradiation with 3.5 Gy, the percentage of tubules showing recovery of spermatogenesis (repopulation index) was 37% in rats that received no hormone treatment. GnRH agonist (GnRH-Ag) treatment with Z oladex or continuous treatment with testosterone markedly stimulated t he recovery of spermatogenesis. When GnRH-Ag treatment was started imm ediately after 3.5-Gy irradiation and maintained for 10 weeks, the rep opulation index was 91%. When an additional 6.5 weeks without further treatment was allowed between the 10-week GnRH treatment and killing t he rats, the repopulation index recovered to 100% and sperm counts to 83 x 10(6). These sperm counts were more than 100-fold higher than tho se in rats not given hormone treatment and 50% of normal nonirradiated control levels. GnRH-Ag for 10 weeks also stimulated spermatogenic re covery in rats irradiated with 6 Gy, even when the start of treatment was delayed until 18 weeks after irradiation. Without GnRH-Ag, the rep opulation index was 0, but in GnRH-Ag-treated rats it was 14.5%. Since all of the hormone treatments suppress intratesticular testosterone, high levels of testosterone may be inhibiting differentiation and thei r suppression may stimulate recovery. Even though the exact mechanism is not yet known, this method may still be applicable for clinical use to activate spermatogenesis in patients rendered azoospermic by irrad iation or possibly by other cytotoxic treatments.