[Reexamination of BT-PABA test (PFD)--on the substrate specificity for pancreatic chymotrypsin in vivo].

It is widely believed that BT-PABA is a specific substrate for pancreatic chymotrypsin, and based on this concept, BT-PABA test is used to evaluate the exocrine pancreatic function. But this test shows unusual clinical results particularly in patients after total pancreatectomy. In order to reevaluate the specificity of BT-PABA for chymotrypsin, we investigated the intestinal influence on this substrate in in vivo and in vitro studies using mongrel dogs under the conditions of complete absence of pancreatic juice in the alimentary tract. In vivo study showed that serum PABA increased after BT-PABA administration in the models of complete absence of pancreatic chymotrypsin and in vitro study demonstrated BT-PABA splitting activity fo jejunum and ileum mucosal homogenate which increased after total pancreatectomy. Hence, we concluded that BT-PABA is not a specific substrate for pancreatic chymotrypsin in vivo in human and in dog.