Immunohistochemistry of the golden hamster pituitary during chronic administration of diethylstilbestrol: a quantitative analysis using confocal laser scanning microscopy

The aim of this study was to examine by immunohistochemistry the morphologi c changes affecting pituitary cell populations in male Syrian hamsters unde rgoing chronic exposure (3 days to 9 months) to diethylstilbestrol (DES). C ell proliferation in the hypophysis was monitored by the immunohistochemica l demonstration of S-phase cells after pulse labeling with 5-bromo-2'-deoxy uridine. Cell proliferation analysis was combined with the identification o f different cell populations by immunostaining with antisera raised against hypophyseal hormones. Sections processed for double-label immunofluorescen ce were examined by confocal microscopy. In the adenohypophysis, the relati ve surface occupied by gonadotrophs and thyrotrophs decreased rapidly durin g the first months of treatment while corticotroph and somatotroph populati ons remained unaffected. Accordingly, the incidence of S-phase cells in the se four cell populations was lower than or similar to control values. In co ntrast, lactotrophs increased gradually during the first month of exposure to DES to reach a maximum value at 2-4 months. At the beginning, this incre ase was primarily due to hyperplasia but later on it also involved cellular hypertrophy. Somatomammotrophs did not seem to be involved in this model. In the pars intermedia, the labeling index of melanotrophs rose rapidly to reach values 5-6 times higher than controls. After 4 months, neoplasms orig inating from the pars intermedia were seen invading both the neuro- and the adenohypophysis. At the end of treatment, the pituitary was markedly enlar ged resulting from the development of an adenoma of the pars intermedia.