The proteolytic effect of pancreatic pseudocyst fluid on vessel walls.

The possible in vivo consequences of proteolytic activity found in pancreatic pseudocyst fluid was investigated experimentally using fresh vessels from rabbit and humans. Proteolytic pseudocyst fluid caused a pronounced and time-dependent decrease in breaking strength of fresh vessels. A destruction of the normal histological architecture and fragmentation of the elastic tissue of the vessel wall paralleled the mechanical findings. The proteolytic digestion was caused by the low-mol-wt fraction of the pseudocyst fluid, corresponding to free proteases. Part of this proteolysis was probably caused by pancreatic proteases, since pancreatic juice also caused a decrease in breaking strength and a destruction of the histologic architecture of the vessel wall. Proteases bound to protease inhibitors, i.e., to alpha-2-macroglobulin, had no proteolytic activity. It is concluded that the proteolytic digestion caused by proteolytic pancreatic pseudocyst fluid may well explain severe complications of pancreatic pseudocysts, like bleeding within the pseudocyst and rupture of the entire pseudocyst wall, although the proteolytic digestion is probably counteracted by a constant regeneration of the pseudocyst wall in vivo.