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.