Hormonal control of seminiferous tubule contractions. A hypothesis of sperm transport from the testicle.

The effects of steroids on the presence or absence and relative magnitude of rat seminiferous tubule contractions were evaluated microscopically. Both 10- and 30-mg implants of estradiol in vivo and concentrations of 10(-8) or 10(-9) M estradiol in vitro depressed the percentage of seminiferous tubules contracting without altering the magnitude of the contraction. Higher doses of both testosterone and dihydrotestosterone in vivo and in vitro maintained the tubular contractions at normal or above normal levels whereas lower doses of these compounds reduced both the percentage and magnitude of the tubules contracting. The results from these experiments suggest that rat seminiferous tubule contractions can be altered by steroids. Testosterone and dihydrotestosterone inhibit the contractions at lower doses and stimulate the contractions at higher doses and thus may regulate the transport of spermatozoa from the rat testicle.