On the Potential Role of Trypsin and Trypsin Inhibitors in Acute Pancreatitis

Abstract

Acute pancreatitis is still a disease with many questions concerning both etiology and pathophysiology in spite of all the research in this field. Many so called “triggers” have been investigated, but none of them have so far been convincingly shown to be the one “trigger”. Trypsin has long been designated as a key-enzyme¹ capable of converting all other pancreatic enzymes into their active forms, and many investigators have shown active trypsin both in peritoneal fluid and in blood in acute pancreatitis.^2,3,4,5 Fig. 1 schematically shows the possible events, when activated trypsin comes free in acute pancreatitis. Within the gland trypsin is directly complexed with PSTI (=pancreatic secretory trypsin inhibitor), but this complex dissociates when it comes in contact with α₂-macroglobulin (α₂-M) and α₁-antitrypsin (α₁-AT). ⁶ Most of the trypsin forms complex with α₂-M, and so is not immunoreactive, and is discharged via the reticuloendothelial system (RES) in a few minutes. A small part of the trypsin complexes with α₁-AT and this complex is immunoreactive, as is also trypsinogen. Active trypsin in the circulation is quickly complexed mostly by α₂-M and a small part with α₁-AT. Fig. 2 shows 45 patients with acute pancreatitis, who all have immunoreactive trypsin along with their raised amylase. With a further development of the radioimmunoassay³, it is possible to separate between trypsinogen and active trypsin bound to α₁-AT, and table 1 shows the values for these 45 patients. The high trypsinogen (normally below 25 μg/1) is a result of leakage. Most patients have rather high proportion of their immunoreactive trypsin as trypsin-α₁-AT, some of them almost 100 %.