Cell Fractionation of Anterior Pituitary Glands from Beef and Pig

Abstract

Fresh anterior pituitary glands from beef and pig were separated by differential centrifugation into subcellular fractions. Nuclei and debris were obtained at 700 g for 15 minutes, secretory granules at 7000 g for 20 minutes, mitochondria at 34,000 g for 15 minutes, and microsomes at 78,000 g for 3 hours. Electron micrographs were taken of the individual fractions. Each fraction was analyzed for nitrogen, pentosenucleic acid (PNA), and phospholipide. Beef and pig anterior lobes were quite similar in their intracellular composition as seen in the subcellular fractions. Succinic dehydrogenase was localized in mitochondria, while alkaline phosphatase was concentrated in the microsomes. A proteinase with pH optimum at 8.2 was exclusively localized, in microsomal and supernatant fractions. Acid phosphatase, acid ribonuclease, and acid proteinase were distributed among the subcellular fractions in another pattern, indicating the presence of a particle type distinct from mitochondria and microsomes. The distribution of cytoplasmic PNA paralleled that of alkaline phosphatase.Cell fracfionation of the anterior pituitary gland by differential centrifugation has been undertaken in this laboratory for the primary purpose of correlating hormonal activities with specific subcellular particles. The results of hormonal distribution will be presented elsewhere. This report deals with the morphological, chemical, and enzymatic criteria which served as a basis for separation of subcellular elements. In the few earlier studies concerned with this particular problem, cell components were arbitrarily separated into sedimentation classes with no regard to morphology (17, 30), on one hand, while others (4), who attempted to separate the components into morphologically homogeneous groups, were generally unsuccessful.