Effects of diethylstilbestrol and propylthiouracil on the rat pituitary. An immunohistochemical and ultrastructural study.

The effects of diethylstilbestrol [(DES) CAS: 56-53-1] and propylthiouracil [(PTU) CAS: 51-52-5] on the pituitary glands of female weanling F344 rats were studied by immunohistochemistry and electron microscopy. Six weeks of PTU treatment resulted in a significant increase in pituitary gland weight and in the percentage of pituitary prolactin (PRL) cells. The percentage of thyroid-stimulating hormone (TSH) cells was slightly increased in PTU-treated rats. DES treatment produced a thirteenfold increase in pituitary gland weight and a significant increase in the percentage of PRL cells as well as in serum PRL levels. Combined PTU-DES treatment increased pituitary gland weight and serum PRL levels, but this increase was less than that observed with only DES treatment. A relative decrease in the percentage of TSH cells was seen after both DES and PTU-DES treatment. Ultrastructural immunohistochemical studies showed two types of PRL cells in the pituitary of all groups. Classical PRL cells with granule diameters of 150-800 nm were most abundant in DES-treated groups, whereas cells with smaller granules, 100-350 nm in diameter, were equally prominent in control groups and after PTU treatment. The results of this study show that while PTU causes a slight increase in pituitary gland weight and in PRL cell numbers, it inhibits estrogen-induced PRL cell hyperplasia. This model can be used to study the effects of PTU on pituitary PRL cell morphology and on the regulation of PRL cell hyperplasia.