Morphometric studies on the testes of rats treated neonatally with oestrogen and subsequently with gonadotrophins and testosterone.

The experiments involved male rats, which were given a single subcutaneous dose of 1 mg stilboestrol on the first day of life. Beginning on day 28, subgroups of the rats received either gonadotrophins or testosterone for 39 days. The weight of the testes, serum luteinizing hormone and testosterone levels were determined while sections of the testes were subjected to morphological analysis and morphometric measurements, based on computerized techniques. The results demonstrated that a single dose of oestrogen caused a reduction in the cross-sectional area of the seminiferous tubules and a reduction in the thickness of the seminiferous epithelium, accompanied by inhibition of spermatogenesis. The number of and area occupied by Leydig cells, as well as the size of their cell nuclei, were also diminished, and the levels of serum testosterone decreased by 73%. All the experimental animals manifested significantly increased serum luteinizing hormone levels. Stimulation with gonadotrophins markedly increased the number of Leydig cells, their size and the size of their cell nuclei. This was associated with significantly increased levels of serum testosterone. Under these conditions, the cross-sectional area of the seminiferous tubules and the thickness of seminiferous epithelium remained less than those in the untreated controls. Following stimulation with testosterone the pattern of the seminiferous tubules resembled that noted after stimulation with gonadotrophins; the number of Leydig cells was markedly reduced but the size of both the cells themselves and of their nuclei approached normal values.