Ultrastructural and enzyme-histochemical studies of the prostate of the dog under the effect of estradiol.

The prostate of 4 mature pure bred Beagles 12 months old was studied 3 weeks following a single i.m. injection of 1 mg estradiol/kg body weight by means of histochemistry (acid and alcaline phosphatase) and electron microscopy. Four 11 months old Beagles served as controls. Estradiol leads to a variable reaction of glandular epithelium. There is an atrophy of active secretory cells, probably due to an inhibition of the release of ICSH by the anterior pituitary lobe, that in turn leads to a deficiency of androgens. The residual secretory function is not sufficient for normal synthesis of secretory granules, recognizable through the decrease in electron density of secretory granules and the extensive loss of activity of acid phosphatase. Under physiologic conditions it corresponds in its localization to the amount of secretory granules lying in the apical portion of the cytoplasm. The basal reserve cells show an ambivalence. Normally under the predominant influence of androgen they do not show any metaplasia, but they differentiate into the secretorely active epithelial cell. Without stimulation by androgens, estradiol leads to a basal cell proliferation with squamous metaplasia particularly in the dorso-lateral lobes close to the urethra. The activity of alcaline phosphatase shows a minor decrease in the capillary endothelium under estradiol. With increasing maturation of the metaplastic squamous epithelium the activity of alcaline phosphatase increases in the upper cell layer.