Serum protease inhibitor capacity for elastase and the severity of pancreatitis

To clarify the relationship between the diminution of the serum protease inhibitor capacity and the severity of pancreatitis, the binding capacity of serum protease inhibitors for exogenous elastase 1 (El) was investigated by gel filtration, the elastase activity of the α₂-macroglobulin (α₂-M)-elastase complex was measured, and the relationship between these findings and the severity of pancreatitis was studied in 13 patients with pancreatic disease and 6 healthy subjects. When 12fT-labeled El was added to the sera of healthy subjects, it bound to α₂-M and α₁-protease inhibitor (α,-PI) with a mean ratio of 72:28. In mild acute pancreatitis (n = 5), the binding capacity of α₂-M was less than that in healthy subjects. In severe pancreatitis (n = 4), most of the exogenous El bound to α₁PI (α₂-M vs. α₁-PI, 13:87). This diminution in the binding capacity of α₂-M correlated well with the severity of acute pancreatitis. In the sera of patients (n = 4) with pancreatic cancer containing much immunoreactive El, the proportion of exogenous El bound by α₂-M and a,-PI (25:75) was similar to that seen in severe acute pancreatitis. A significant inverse relationship between the binding capacity of α₂-M and the activity of the endogenous elastase bound to α₂-M was seen in various pancreatic diseases. These findings suggest that in acute pancreatitis, the decreased binding capacity of serum α₂-M and the increased enzymatic activity of the α₂-M-protease complex correlate with the severity of the pancreatitis. In pancreatic cancer, however, this is not necessarily the case.