Ultrastructure and immunohistochemistry of the lateral prostate in aged rats.

Ultrastructural, histological, and immunohistochemical studies were performed on lateral prostates of 1) aged rats from different strains, 2) rats permitted different levels of sexual activity, and 3) castrated rats. Antibodies against the following proteins were used as immunohistochemical markers: SVS II from seminal vesicle, LP 28 from lateral prostate, acid phosphatase isoenzymes from ventral prostate, transglutaminase from coagulating gland, and a commercial monoclonal antibody against cytokeratin. SVS II is a marker of lateral prostatic secretion, while immunoreactions to LP 28 and acid phosphatase (pI 7.1) were cytoplasmic. In aged animals the amount of intracellular secretion is decreased, and focally metaplastic transformation can be visualized by using immunohistochemical markers. Epithelial ultrastructure varied considerably with experimental conditions. Intensive sexual activity resulted in increased polymorphism and increased number of secretory granules within the glandular cells, while castration was followed by a rapid loss of secretory material. Also, in rats older than 10 months, a reduction in the number of secretion granules was common. The epithelium developed a positive immunoreaction to transglutaminase antibodies that were not observed in juvenile glands. Cells, presumably macrophages, which had an intense immunoreactivity for transglutaminase, were increased in number both within and outside the prostatic acini of aged rats. The possible interaction between secretory SVS II, a substrate of transglutaminase, the release of this enzyme from macrophages or its reflux from coagulating glands, the spontaneous cellular exfoliation that is due to decreased androgen levels, and dietary noxae may be of importance in the development of lateral prostatic nonbacterial inflammation in aged rats.