Ultrastructural study of regressed and reactivated testes from Soay rams.

Testes from 4 sexually active and 4 sexually regressed adult Soay rams housed under artificial lighting were examined. The reduction in testis weight during sexual regression (reduced to 35% of active) was due to a decrease in the diameter of the seminiferous tubules with extensive involution of the basement membrane, a marked reduction in the number of germ cells maturing beyond the spermatocyte stages, and a general disorganization of all but the most basal region of the seminiferous epithelium. The Sertoli cells contained large lipid droplets and deposits of lipochrome pigment and large necrotic bodies. The Leydig cells showed some reduction in content of smooth endoplasmic reticulum during sexual regression although they were approximately 30 times less active steroidogenically as judged by the peripheral levels of testosterone. Blood levels of LH and FSH were significantly reduced compared to those in sexually active animals, while the prolactin levels were much increased.