TESTOSTERONE WITHDRAWAL PROMOTES STAGE-SPECIFIC DETACHMENT OF ROUND SPERMATIDS FROM THE RAT SEMINIFEROUS EPITHELIUM

Testosterone (T) has been shown to be essential for the completion of spermiogenesis. Our previous studies showed that when intratesticular T was suppressed for 11 wk, the conversion of round spermatids between stages VII and VIII of the spermatogenic cycle was markedly suppresse d and that elongated spermatids were undetectable. The fate of the rou nd spermatids that did not proceed through this conversion was unclear . The current study aimed to investigate this T-dependent loss of roun d spermatids during stages VII and VIII. Adult male Sprague-Dawley rat s received 24-cm T implants for 1 wk to suppress LH while maintaining spermatogenesis. The T24 implants were removed and replaced with 3-cm T plus 0.4-cm estradiol CTE treatment) to suppress intratesticular T a nd spermatogenesis, and animals were killed at 0 and 4 days and 1, 2, 3, 4, and 6 wk later. The number of homogenization-resistant elongated spermatids in the testis was counted, and round spermatid populations in stages VII and VIII were quantified using stereological techniques . The hourly production rates (HPR) were calculated, and a ratio was m ade between the HPR of round spermatids in stages VII and VIII to asse ss the efficiency of their conversion through these stages. Testicular T levels were suppressed to 2-4% of control values by TE treatment. A fter 2 wk of TE treatment, the number of homogenization-resistant elon gated spermatids was significantly suppressed, falling to < 0.5% of th e control value by 6 wk. The HPR of round spermatids in stages VII and VIII was not affected by up to 2 wk of TE treatment, nor was the conv ersion between these stages interrupted. After 3 wk of TE treatment, t he HPR of round spermatids in stages VII and VIII was significantly su ppressed, as was the conversion between these stages, the ratio fallin g to 27% of the control value by 6 wk. In rats treated with TE, histol ogical examination of the cauda epididymidis showed occasional round s permatids after 3 wk of treatment, and large numbers after 6 wk. We co nclude that the failure of round spermatids to complete spermiogenesis following T withdrawal is due to stage-specific detachment of round s permatids between stages VII and VIII.