Particles resembling C-type oncornaviruses in normal rat prostate.

A large number of particles resembling oncornaviruses were observed in the ventral lobe of a normal rat prostate. The particles were seen budding into the intercellular spaces of the epithelial lumen cells. They exhibited features morphologically similar to immature C-type particles, with an electron-lucent center and a diameter of approximately 100 nm. Neither intracellular A-type particles nor mature C-type particles were observed. This is the first report of particles resembling oncornaviruses in normal rat prostatic tissue.