Induction of enrichment of the stages of the seminiferous epithelial cycle in prepubertal rats.

The aim of the present study was to examine the feasibility of inducing enrichment of the stages of the seminiferous epithelium in prepubertal male rats produced by vitamin A-deficient (VAD) females that had received a supplement of a marginal level of retinol. Seventy-day-old retinoic acid-supplemented VAD female rats were given daily doses of 5, 10, or 20 micrograms retinol for 2 wk. Breeding of these females resulted in the production of viable offspring in litters of normal size. Subsequently, male rats so produced (VAD males) were given a single injection of 10 or 20 micrograms retinol at 10 or 20 days of age, fostered by normal lactating females, and weaned at 25 days of age. These rats were maintained on normal rat chow thereafter. At 10 days of age, active spermatogonial proliferation was not seen in the testes of VAD males born to VAD females receiving a 5- or 10-micrograms daily dose of retinol. Concurrently, cells resembling gonocytes were frequently seen, and pre-type A spermatogonia were seen in over 80% of the tubules examined. By 20 days of age, the presence of active spermatogonial proliferation was demonstrated by the appearance of preleptotene spermatocytes, but these failed to differentiate further. Spermatogenesis of the VAD males born to VAD females given a daily dose of 20 micrograms retinol appeared to be normal at both 10 and 20 days of age. Forty days after the retinol replacement, the testes of VAD males born to VAD females given a daily dose of 5 or 10 micrograms retinol were enriched with specific stages of the seminiferous epithelium while other stages were absent. The stages enriched were affected by the dose of retinol administered and the age when retinol replacement began. The stage enrichment in these animals persisted for at least 135 days. Seminiferous epithelium of the VAD males born to the VAD females receiving a 20-micrograms daily dose of retinol was not stage-enriched. Northern blot analysis of testicular RNA revealed stage-dependent changes in the steady-state level of mRNA for spermatid protamine and Sertoli cell androgen-binding protein (ABP). Results of this study demonstrate the feasibility of inducing enrichment of seminiferous stages in prepubertal rats. The production of this animal model is cost-effective in that it saves in time and animal maintenance.(ABSTRACT TRUNCATED AT 400 WORDS)