Synthetic peptides in the diagnosis of exocrine pancreatic insufficiency in animals

Abstract

SUMMARY A new approach in the diagnosis of exocrine pancreatic insufficiency has been evaluated in animals. The method involves the oral administration of a chymotrypsin-labile peptide which contains p-aminobenzoic acid (PABA) as a tracer group. In the small bowel in the presence of chymotrypsin, the PABA is split from the peptide and is rapidly absorbed. The amount of PABA (as total aromatic amines) recovered in the urine during the six hours after the dose is used as an index of exocrine pancreatic function. The procedure has been shown to be reliable in detecting surgically induced pancreatic insufficiency in rats, swine, and dogs.A new tubeless test for exocrine pancreatic insufficiency was suggested to us by Dr Norton J. Greenberger. Preliminary studies showed the test to be highly reliable in detecting pancreatic deficiency in animals (Imondi, Stradley, Wolgemuth, and Brown, 1971). In this procedure a synthetic peptide composed of an aromatic amino acid and a readily absorbable tracer group, p-aminobenzoic acid (PABA), is administered orally. In the presence of chymotrypsin, the peptide is split with the liberation of PABA which is absorbed from the gut, undergoes conjugation, and is excreted in the urine. The amount of PABA (aromatic amines) in the urine is used as a measure of exocrine pancreatic function. Methods ANIMALSExocrine pancreatic insufficiency was produced surgically in male and female Sprague-Dawley rats (200-400 g), mongrel dogs (5-10 kg), and West African Guinea swine (8-20 kg). The rats were anaesthetized with ether and the common bile duct was doubly ligated and sectioned near its attachment to the duodenum. These animals are referred to in this paper as B-PDL rats to denote the exclusion of both bile and pancreatic juice from the intestine.These rats, in which bile was excluded from the intestine, were prepared by ligating the bile duct just below the hilus of the liver (Grossman, 1958). An 18-hour recovery period was allowed before administering the peptide to the rats. Pancreatic Received for publication 2 June 1972. duct ligation and section (Pekas, Hays, and Thompson, 1964) was performed in the swine under halothane anaesthesia. These animals, referred to as PDL, were allowed a minimum of three postoperative recovery days before drug testing. Dogs were made exocrine pancreatic deficient by ligating the pancreatic ducts and separating the pancreas from the duodenum with omentum (Grossman, 1962). Studies in dogs were not begun until at least one week after surgery. The surgical procedures did not significantly affect the ability of the animals to absorb and excrete orally administered PABA. TEST PROCEDURE in vivo Animals to be tested were fasted overnight. The test peptide was administered orally as an aqueous solution of its sodium salt. After dosing the animals were confined individually to metabolism cages. Food was withheld, but water was allowed ad libitum. Urine collections were made at the times stated in each experiment. The total aromatic amine concentration of the urine...

The Oral Pancreatic Function Test with N-Benzoyl-L-tyrosyl-p-aminobenzoic Acid: Acute Toxicity and Effects of Renal Function on this Test

“…The amount of p-aminobenzoic In 1972 Imondiet al (1) reported successful experiacid eliminated in the urine during a given period serves merits in animals with a new oral function test. The as a measure of exocrine pancreatic secretion.…”

STUDIES ON THE ABSORPTION OF THE PANCREATIC FUNCTION TEST PEPTIDE, N‐BENZOYL‐L‐TYROSYL‐p‐AMINOBENZOIC ACID, AND RELATED COMPOUNDS BY ISOLATED RAT SMALL INTESTINE

“…Imondi, Stradley & Wolgemuth, 1972;Gyr, Wolf, Imondi & Felsenfeld, 1975;Gyr, Stalder, Schiffman, Fehr, Vonderschmitt & Fahrlaender, 1976;Arvanitakis & Greenberger, 1976). The peptide is hydrolysed in the small intestine by pancreatic chymotrypsin; the liberated p-aminobenzoic acid (PABA) is absorbed and subsequently excreted in the urine.…”

“…Animal and human studies have already indicated that this test can distinguish between controls and subjects with exocrine pancreatic insufficiency (e.g. Imondi et al 1972;Gyr et al 1976;Arvanitakis & Greenberger, 1976), although malabsorption of PABA may give false abnormal results unless a test of intestinal absorption is made concurrently Stradley, Stern & Heinhold, 1979;Mitchell, Humphrey, Bullen, Kelleher & Losowsky, 1979).…”

Unresponsiveness of GH and cortisol to insulin-hypoglycemia in a patient with sub-total pancreatectomy.

“…Serum amylase was 168 IU/1, 92% of which was the salivary type. PFD test (Imondi et al, 1972) was carried out and showed only 56% excretion of p-aminobenzoic acid in the urine, demonstrating the absence of functional pancreas. Moreover, no definite demonstration of the residual pancreas was obtained not only by CT-scanning but also by ultrasonography, confirming previous subtotal pancreatectomy.…”