EFFECTS OF LIGATION OF THE PANCREATIC DUCT UPON THE ACTION OF SECRETIN AND PANCREOZYMIN IN RABBITS WITH A CORRELATED HISTOLOGICAL STUDY

Pancreatic interstitial pH in human and feline chronic pancreatitis

BACKGROUND & AIMS

Advanced chronic pancreatitis is associated with a reduction in pancreatic blood flow. To determine the physiological significance of this decrease, pancreatic interstitial pH was measured in a model of obstructive chronic pancreatitis in cats and in patients with chronic pancreatitis.

METHODS

In cats, pancreatic interstitial pH and blood flow were measured serially under basal conditions and after secretory stimulation as chronic pancreatitis evolved. Basal pancreatic interstitial pH was also measured in patients undergoing an operation for chronic pancreatitis or periampullary cancer (controls).

RESULTS

In normal cats, pancreatic interstitial pH was 7.41 +/- 0.01 and blood flow was 124 mL.min-1.(100 g pancreas-1). With the evolution of chronic pancreatitis, interstitial pH and blood flow progressively decreased to 7.21 +/- 0.04 (P < 0.007) and 75 +/- 11 (P < 0.007), respectively. From 1 to 2 weeks, secretory stimulation reduced pancreatic interstitial pH and blood flow further, but as secretory function was lost, this effect disappeared. In patients with chronic pancreatitis, the interstitial pH was lower (7.02 +/- 0.06) than in controls (7.25 +/- 0.04; P < 0.05).

CONCLUSIONS

These observations are consistent with the hypothesis that, in chronic pancreatitis, acidic metabolites associated with pancreatic secretion accumulate within the pancreas, probably because of impaired blood flow.

Effect of chronic partial pancreatic duct obstruction on pancreatic duct secretory pressure and permeability in cats

Pancreatic secretion during pancreatic duct obstruction results in increased duct pressure. The normally impermeable pancreatic duct becomes permeable to macromolecules the size of pancreatic enzymes after secretion against obstruction. Permeability and morphologic changes may be related to increased secretory pressure during obstruction. We obstructed the main pancreatic duct of cats by 25-100% of its luminal diameter in different groups for 2, 7, or 28 days. Permeability to macromolecules of fluoresceinated dextran (FD) was greatest in cats with less than 75% obstruction compared with cats with greater than 75% obstruction regardless of the duration of obstruction. The frequency of permeability to FD decreased significantly as both the degree and duration of obstruction increased. Secretory pressure also changed according to degree and duration of obstruction. The highest pressures were in cats with complete obstruction at 2 days. Pressure decreased as the degree and duration of obstruction increased. Histologic changes such as acinar lobular atrophy and interstitial fibrosis were most severe in cats with the greatest degree and duration of obstruction. Pressure and permeability changes indicate a greater sensitivity to increased duct pressure than previously thought. These observations may clarify the role of pancreatic duct obstruction in pancreatic disease.

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.

Pancreatic secretions as a clue to the presence of pancreatic cancer

Pancreatic secretory function is abnormal in at least 90% of patients with pancreatic cancer. These abnormalities may be due to direct involvement of the secretory cells by the malignant process and/or the effects of pancreatic duct obstruction. There is no specific stimulus (secretin and/or cholecystokinin, CCK, or CCK-like hormones) of pancreatic secretion that is clearly superior to any other as a test of pancreatic function. Pancreatic secretion is abnormal in animal models of pancreatic cancer and secretory abnormalities antedate the histologic appearance of the cancer. A decrease in protein secretion after CCK stimulation is the most significant finding in experimental partial pancreatic duct obstruction (the condition most commonly seen in pancreatic cancer). In the absence of any identifiable high-risk group within the population, it is unlikely that the testing of pancreatic function provides a means for the earlier diagnosis of pancreatic cancer.