Pancreatic juice gamma-glutamyltransferase, alanine transaminase, and alkaline phosphatase in pancreatic disease

Secretion of gamma-glutamyltranspeptidase by the pancreas: evidence for a membrane shedding process during exocytosis

Gamma Glutamyltranspeptidase (GGT) is a membrane-bound enzyme involved in glutathione metabolism. It is present in rat exocrine pancreas at a level which is only exceeded by the kidney. It has been previously shown that most of the enzyme activity is located in the apical area of the acinar cell, more precisely at the level of zymogen granules and plasma membrane. The aim of the present study was to examine the secretory behavior of that enzyme. Under resting conditions, in vivo, high levels of GGT were found in pancreatic juice and its level was not related to protein concentration. Under secretin infusion, a relatively constant level of GGT was released, and again, there was no correlation between enzyme activity and protein concentration. Following a bolus injection of caerulein, an analog of cholecystokinin, marked and concomitant rises in protein and GGT levels were observed. Ultracentrifugation, as well as gel filtration on Sepharose 4B, demonstrated that the enzyme was not released in a soluble form. This observation is in agreement with in vitro determinations on isolated zymogen granules showing that GGT is totally associated with the ZG membrane and undetect-able in the content of these organelles. The present data show that 1 degree GGT is released from the rat pancreas acinar cells in a particulate form; 2 degree GGT release is elicited by hormonal stimulation coinciding with the exocytotic release of secretory proteins. Our observations lead us to propose that in rat pancreas, ZG membrane fragments are released along with secretory proteins during exocytosis.

Effect of duct obstruction on histology and on activities of gamma-glutamyl transferase, adenosine triphosphatase, alkaline phosphatase, and amylase in rat pancreas

The effect of pancreatic duct obstruction on the activities of amylase and three nonexocrine pancreatic enzymes was studied in the rat. gamma-Glutamyl transferase (GGTase) activity, which is localized primarily in the plasma membrane of acinar cells, disappeared from the acinar basolateral plasma membrane and declined in specific activity by 80% over a seven-day experimental period. Mg-ATPase, localized primarily in the apical plasma membrane of acinar cells, simultaneously declined in activity in acinar cells but increased in activity in connective tissue. Mg-ATPase specific activity rose 3.5-fold. The histochemical results showed that the ductlike cells resulting from obstruction were derived primarily from acinar cells. Alkaline phosphatase (APase) activity, which is localized in vascular endothelium and the stroma of interlobular ducts, exhibited a dramatic increase in the periacinar, periductal, and interlobular stroma, and specific activity rose 11-fold. Amylase-specific activity declined as did the protein to DNA ratio. Gel electrophoresis showed that the amount of zymogen granule polypeptides declined after duct obstruction, whereas a few other polypeptides increased in amount.

The intraductal secretin test: an adjunct to ERCP

The intraductal secretin test is an important diagnostic study. It enables the physician to determine the pancreatic secretory function in patients with known pancreatitis and to confirm the diagnosis of pancreatitis in many patients with indeterminate upper abdominal pain in whom ERCP and other diagnostic studies are normal. The IDST also provides the endoscopist and biochemist a new means to establish discriminating tests in differential diagnosis of pancreatic cancer and pancreatitis and to study the physiology of pancreatic secretion.

Comparative studies on viscosity and concentration of protein and hexosamine in pure pancreatic juice

In order to investigate the cause of an increase in viscosity of pancreatic juice in patients with chronic pancreatitis, we performed comparative studies on voscosity and concentration of protein, hexosamine, three hydrolytic enzymes (amylase, chymotrypsinogen and lipase), calcium and gamma-Glutamyltranspeptidase in pure pancreatic juice. Pure pancreatic juice (PPJ) was obtained from seven control subjects, 10 patients with probable chronic pancreatitis and six patients with definite chronic pancreatitis by means of endoscopic retrograde catheterization of the papilla. Specimens were collected in ice-cooled tubes during the initial four-minute period and thereafter at two-minute intervals for 20 minutes after a rapid intravenous injection of secretin (Eisai Secrepan, 1 U/kg of body weight) and then at one-minute intervals for 10 minutes after a rapid intravenous injection of pancreozymin (Boots, 1 U/kg of body weight). It was demonstrated that the viscosity of PPJ was closely related to the concentration of hydrolytic enzyme protein, hexosamine and the presence of mucous substance and protein plugs.