Fine structural and functional study of the prostatic complex of the guinea pig

The fine structure of the prostate gland of the guinea pig was studied by electron microscopy. The lateral lobe was characterized by tall columnar epithelium which formed various degrees of foldings. The epithelial cells had well developed granular endoplasmic reticulum (GER). The cisternae were closely packed and often arranged in concentric configuration in the basal cytoplasm. The apical cytoplasm was characterized by a large Golgi and prominent secretory granules. The luminal border typically contained microvilli. Fusion of the secretory granules with the luminal membrane were observed. The secretion in this lobe is believed to be triggered by a merocrine mechanism. The glandular cells of the dorsal prostate were characterized by well-developed and dilated GER. Most cells had no secretory granules and the luminal surface was endowed with microvilli. It is believed that in these cells the secretion is stored in the cisternae and may be discharged directly into the lumen. A small number of cells in the dorsal prostate showed large dense secretory granules in the apical region. Secretion in this group of cells, as in the cells of the lateral prostate, is believed to be produced by a merocrine mechanism. The coagulating gland on the other hand, had sparser GER and less dilated cisternae. The cells contained no secretory granules and usually had a small Golgi. Apical blebs were commonly found in these cells. Apical blebs have been observed to pinch off from the apical cytoplasm and to release the small sacs of secretory material into the lumen. This is an apocrine mechanism of secretion.