Is There a Local Feedback from the Seminiferous Tubules Affecting Activity of the Leydig Cells?1

Silastic tubing containing cyproterone acetate or braided silk sutures impregnated with WIN-18446 or ORF-1616 were inserted under the tunica albuginea of the testes. Spermatogenesis was suppressed in tubules in the immediate vicinity of the implants, but the interstitial tissue associated with the atrophic tubules appeared more abundant. Electron micrographs showed hypertrophy of the smooth endoplasmic reticulum and other evidence of Leydig cell stimulation. Interstitial tissue in the same testis at a distance from the implants showed no evidence of stimulation. The results are discussed in relation to the possibility of a local feedback from the tubules modulating sensitivity of the Leydig cells to circulating gonadotropin.