Protein secretion in the rat ventral prostate and the relation of golgi vesicles, cisternae and vacuoles, as studied by electron microscope radioautography.

Abstract

AbstractProteins, including enzymes such as acid phosphatase, are among a variety of substances secreted into semen by the prostate gland. The formation, intracellular transport, and discharge of protein components of prostatic secretion were studied in the rat ventral prostate following an injection of leucine‐3H. Samples were prepared for light and electron microscope radioautography at intervals ranging from four minutes to two hours after the injection. In samples prepared four or ten minutes after administration of the precursor, most of the silver grains overlay the rough endoplasmic reticulum. Beginning 30 minutes after the injection, while label associated with the endoplasmic reticulum was declining, the proportion of grains over the Golgi apparatus began to increase, reaching a maximum in one‐hour samples. Secretory vacuoles at the apical ends of the cells became heavily labeled two hours after administration of the leucine‐3H. Labeling of secretions in the lumen of the prostatic alveoli was observed in samples taken two hours after the injection. These results indicate that secretory proteins in the prostate are synthesized in the rough endoplasmic reticulum, transported to the Golgi apparatus, and packaged into secretory vacuoles, which move to the apical ends of the cells and release their contents to the lumen. Additional analysis of the pattern of labeling of different elements of the Golgi apparatus suggests that some protein is transported sequentially from Golgi vesicles to stacks of cisternae and finally into Golgi vacuoles. Radioactive secretory proteins move through prostatic cells more slowly than through the seminal vesicle epithelium of the same animals. The main mode of protein secretion in the prostate appears to be a merocrine type, since apical protrusions such as have been suggested to participate in an apocrine form of secretion were observed infrequently and did not become heavily labeled.