Glutathione synthesis in the exocrine pancreas

Glutathione is essential for cellular cytoprotection, and in the exocrine pancreas, it is required for digestive enzyme synthesis. The purpose of these studies was to measure the capacity of the exocrine pancreas to synthesize glutathione, determine whether the pancreatic transsulfuration pathway has a role in providing cysteine needed for glutathione synthesis, and determine whether the glutathione synthetic capacity of the pancreas responds to pathologically relevant stresses. The activity of gamma-glutamylcysteine synthetase, the key regulatory enzyme for glutathione synthesis, was 3.56 +/- 0.29 mU/mg protein in the pancreas of fed rats, compared to 31 +/- 4 in the liver and 116 +/- 5 in the kidney. Studies using dispersed rat pancreatic acinar cells showed that the exocrine pancreas synthesizes glutathione from precursor amino acids and that the transsulfuration pathway is functionally intact in the pancreas and may serve as an important source of pancreatic cysteine. In mice, pancreatic gamma-glutamylcysteine synthetase activity was induced 37% by corn oil, 77% by ethanol, and 88% by both treatments. Thus, the glutathione synthetic capacity of the pancreas is quantitatively less than that of the kidney or liver, but its key regulatory enzyme responds dynamically to pathologically relevant metabolic stresses, suggesting that glutathione is a key pancreatic cytoprotectant.