Sulfate incorporation by mouse synovial cells in vivo.

Mouse synovium was examined autoradiographically at various postinjection to determine the pattern of 35S utilization. Synovial cells incorporated 35S in a manner consistent with synthesis and secretion of sulfated macromolecules. Ultrastructural examination demonstrated two cell populations, one with a structure indicative of phagocytic function, the other with a structure typical of secretory activity.

Incorporation of leucine by mouse synovial cells in vivo.

Following 3H-leucine administration, mouse synovium was examined autoradiographically at various postinjection times to determine whether the pattern of 3H-leucine utilization in vivo is comparable to that previously reported in vitro. Synovial cells incorporated 3H-leucine in significantly greater amounts than other cells examined. The pattern suggested intracellular incorporation, followed by secretion.

Sulphate metabolism in the exocrine pancreas. II. The production of sulphated macromolecules by the mouse exocrine pancreas.

The types of sulphated macromolecules produced by the exocrine pancrease were investigated. To determine whether this tissue utilized inorganic sulphate for protein production, the in-vitro behaviour of material labelled with 35S-sulphate was compared with material labelled with [3H]leucine (secretory proteins). While incubating tissue slices in the presence of cycloheximide resulted in an immediate and nearly complete inhibition of protein synthesis, a similar decrease in production of sulphated material was not observed until after 2 h of incubation in the presence of the drug. Likewise, the kinetics of pilocarpine-induced discharge of radioactive material from pancreatic slices pulse-labelled with either 3H-Leu. or 35S-sulphate was compared. During the first 90 min of stimulation sulphated macromolecules were detected in chase medium 10-15 min prior to the appearance of 3H-labelled secretory proteins. That in-vitro behaviour of sulphated material differed from radioleucine-labelled material is indicative of the fact that the pancreas utilizes inorganic sulphate for the production of macromolecules other than secretory proteins. Lipid and proteoglycan fractions were prepared from pancreatic tissue 4 h after intraperitoneal injection of radiosulphate. The recovery of a significant amount of radioactivity in both fractions deomonstrated the ability of the pancreas to use inorganic sulphate for the production of both sulphated lipids and sulphated proteoglycans. The possible function of sulphated macromolecules in pancreatic secretion is discussed.

Intracellular transport of sulfated macromolecules in parotid acinar cells.

Intracellular transport of sulfated macromolecules in parotid acinar cells was investigated by electron microscopic radioautography after injection of 35S-sulfate. Ten minutes after injection radiosulfate was concentrated in the Golgi region. By 1 hr, much of the radioactive material had been transported to condensing vacuoles. These vacuoles were subsequently transformed into zymogen granules which contained almost 70% of the radioactivity 4 hrs after injection. These results indicate that, in addition to its packaging function, the Golgi apparatus in parotid acinar cells is capable of utilizing inorganic sulfate for the production of sulfated macromolecules. These molecules, following an intracellular route similar to that taken by digestive enzymes, become an integral component of zymogen granules. The possibility that sulfated macromolecules play a role in exocrine secretion by aiding in the packaging of exportable proteins is discussed.

Sulfate metabolism in pancreatic acinar cells.

The metabolism of inorganic sulfate in pancreatic acinar cells was studied by electron microscope radioautography in mice injected with sulfate-(35)S. Labeled sulfate was concentrated in the Golgi complex at 10 min. Within 30 min, much of the radioactive material had been transferred to condensing vacuoles. These were subsequently transformed into zymogen granules. By 4 hr after injection, some of the zymogen granules with radioactive contents were undergoing secretion, and labeled material was present in the pancreatic duct system. The Golgi complex in pancreatic acinar cells is known to be responsible for concentrating and packaging digestive enzymes delivered to it from the endoplasmic reticulum. Our work demonstrates that the Golgi complex in these cells is also engaged in the manufacture of sulfated materials, probably sulfated mucopolysaccharides, which are packaged along with the enzymes in zymogen granules and released with them into the pancreatic secretion.