An ultrastructural and morphometric study of the testes in 15-, 22-, 45-, and 90-day-old neonatally estrogenized rats was performed. At 45 days of age, the Sertoli cells appeared immature in estrogenized rats, whereas they were fully mature in the controls. This finding might be related to a deficiency in gonadotropins and androgens during the postnatal period. In 90-day-old estrogenized rats, however, Sertoli cell maturation had occurred, which might be attributed to a recovery of hormone levels. Cytoplasmic alterations, however, such as vacuolation, were present at this age. The morphometric study revealed decreased testicular and tubular volumes as well as decreased mean tubular diameters in the estrogenized animals. In contrast, the absolute tubular length increased more in these animals than in the controls during the period from 15 to 90 days of age. This lengthening process might be related to the large number of hypercurved tubules in the estrogenized rats.

In a morphometric study on the ventral prostate and seminal vesicles in the rat, we investigated the changes in fibromuscular stroma, glandular epithelium, and glandular lumen. Animals were studied at 15, 30 and 45 days of age. The rapid prepubertal growth started earlier in the ventral prostate than in seminal vesicles. In addition, the effects of neonatal administration of estrogens on the different tissue compartments were studied, comparing rats that had been castrated and/or treated with estrogen at birth to intact animals at 15 days of age. Estrogens caused a decrease in the volume of the glandular epithelium and increased the volume of the fibromuscular stroma in both ventral prostate and seminal vesicles. Castration partially abolished the estrogen-induced growth of the stroma, which suggests that the growth is dependent on testicular factors. The difference in proportion of the fibromuscular stroma between the two glands is evidence that the size of the whole seminal vesicles has increased whereas the size of the ventral prostate has decreased.

The presence of increased numbers of mast cells in the testis of adult neonatally estrogenized rats is reported. The histometric study revealed significant differences between control and estrogenized animals for two ages considered (45 and 90 days). This increase might be related with the development of connective tissue in estrogenized rats.