Spermiation failure is a major contributor to early spermatogenic suppression caused by hormone withdrawal in adult rats

Spermiation is the process by which mature sperm are released from the Sert oli cell into the lumen of the seminiferous tubule. Previous studies have s hown that FSH and LH/testosterone suppression causes a significant increase in the degeneration of mature elongated spermatids. The purpose of this st udy was to investigate the extent to which spermiation failure contributes to the overall failure of spermatogenesis during hormone suppression. We us ed in, vivo models to selectively suppress either FSH, by passive immunizat ion, and or testosterone, by administration of SILASTIC brand (Dow Coming) testosterone and estradiol implants to suppress LH and testicular testoster one production. Stereological quantitation of the number of step 17-18 sper matids before spermiation and the number of step 19 spermatids retained wit hin the epithelium after spermiation showed that 2% of spermatids failed to spermiate in control animals, and 11% and 14% of spermatids failed to sper miate after 1 week of FSH inhibition or testosterone suppression, respectiv ely. After 1 week of combined FSH and testosterone withdrawal, 50% of the s permatids in the testis failed to be released. A time course of testosteron e suppression showed that after 4-5 weeks over 90% of spermatids failed to spermiate. We conclude that spermiation is highly sensitive to hormone supp ression, with T and FSH acting synergistically to support spermiation, and that spermiation inhibition is a potential target for contraception.