THE DURATION OF THE CYCLE OF THE SEMINIFEROUS EPITHELIUM IS ALTERED BY ADMINISTRATION OF 2,5-HEXANEDIONE IN THE ADULT SPRAGUE-DAWLEY RAT

The duration of the cycle of the seminiferous epithelium is believed t o be under genetic control rather than being influenced by other facto rs. However, the frequencies of certain spermatogenic stages-reflectin g their relative durations-can be altered under various conditions inc luding treatment with the n-hexane metabolite, 2,5-hexanedione (HD). T o investigate whether HD administration alters the duration of the spe rmatogenic process, adult Sprague-Dawley rats were exposed to vehicle (n = 20) or 1% HD dissolved in the drinking water (n = 40) throughout a period of 29 days. On day 17, 100 mg/kg of 5-bromodeoxyuridine (BrdU ) was given intraperitoneally; 3 hours later one testis was removed, a nd the remaining testis was excised 12 days later. BrdU was localized in Bouin's-fixed, Paraplast-embedded testes using immunogold-silver-st aining, and sections were counterstained with periodic acid-Schiff and hematoxylin to permit identification of the spermatogenic stages. HD treatment reduced weights of body, testis, and epididymis (P < 0.05) b ut had no effects on serum levels of follicle-stimulating hormone or t estosterone. The seminiferous epithelium was vacuolized, and spermatog enesis was affected to various degrees. HD significantly reduced the f requency of stage VII tubules (P < 0.01) and increased the frequency o f stage IX and stage X tubules (P < 0.05). Furthermore, HD reduced the stage-dependent progression of BrdU-labeled germ cells. By day 29, Br dU-positive germ cells were seen in 13% of stage IX control tubules, w hereas in HD-treated animals BrdU-labeled germ cells were not present in stage IX tubules and were found in only 2-3% of stage VIII tubules; the calculated duration of the spermatogenic cycle was significantly increased (P < 0.01) in the HD-administered animals (13.43 +/- 0.10 vs . 12.37 +/- 0.05 days). These findings demonstrate (1) that the durati on of the cycle of the seminiferous epithelium can be altered experime ntally in the adult Sprague-Dawley rat and (2) that changes in the fre quency of spermatogenic stages can be associated with a change in the duration of the spermatogenic process.