[Diagnosis of exocrine pancreatic malfunction with a synthetic peptide specific for chymotrypsine (author's transl)]

Influence of gastric emptying on the PABA test

Serum and urine PABA curves monitored in 13 healthy volunteers were analysed and compared with curves from 11 healthy volunteers after administration of the gastrokinetic agent domperidone. Both in serum and in urine less variation in the PABA curves was observed after domperidone. Results without domperidone were subdivided in a group with normal gastric emptying (I) and a group with slow gastric emptying (II), based upon the time at which the serum PABA peak was found. Maximal serum PABA concentration, serum PABA at t = 60 min, lagphase and t1/2 for urinary excretion, and % PABA excretion from 0-3 h, 3-6 h and 0-6 h differed significantly between the two groups. Instead, no differences were found between subgroup I and volunteers after concomitant domperidone administration. In summary, PABA test results in serum and urine are influenced by variations in gastric emptying. Domperidone corrects for delayed gastric emptying and thereby narrows the range of normal PABA excretion values.

Chymotrypsin: molecular and catalytic properties

A review on the peptide hydrolase chymotrypsin gives some characteristics concerning the structure, specificity, mechanism of activation from its precursor and catalytic activity. Problems of the active sites, allosteric alterations, changes of conformation, different behaviour against types of substrates, and suggested kinetics are shown in some detail. Finally, the diagnostic role of this serine proteinase is mentioned.

Value of serum PABA as a pancreatic function test

In a total of 71 subjects (19 controls, 24 patients with non-pancreatic gastrointestinal disease, and 27 patients with pancreatic disease) an oral pancreatic function test using N-benzoyl-L-tyrosyl-PABA (BT-PABA) was performed with simultaneous determination of the serum para-aminobenzoic acid (PABA). Urinary excretion of PABA was significantly less (p less than 0.001) in patients with chronic pancreatitis (n = 12) and pancreatic carcinoma (n = 10) than in controls and in patients with non-pancreatic disease. The serum concentration curve in patients with chronic pancreatitis was significantly flattened (p less than 0.001) compared with that of the control group and the patients with non-pancreatic gastrointestinal disease. The discrimination between the controls and the patients with chronic pancreatitis was best at 120 minutes after administration of BT-PABA (lower limit of normal: 2.8 micrograms/ml). The results of our study show that determination of PABA serum concentration two hours after administration of BT-PABA is as valuable an index of pancreatic function as the urinary excretion of PABA.

Assessment of exocrine pancreatic function by oral administration of N-benzoyl-L-tyrosyl-p-aminobenzoic acid (Bentiromide): 5 years' clinical experience

Exocrine pancreatic function was assessed in 588 subjects by oral administration of 1 g of the chymotrypsin-labile peptide N-benzoyl-L-tyrosyl-p-aminobenzoic acid (Bentiromide) from 1974 to 1979. The pancreatic function test (PFT) was performed in 126 controls, 217 patients with pancreatic diseases, 196 patients with various non-pancreatic gastrointestinal disease, 18 patients with renal disease and 31 patients with various other diagnoses. In 62 of 72 patients (86 per cent) with chronic pancreatitis and in 19 of 25 (76 per cent) with pancreatic carcinoma, the excretion of p-aminobenzoic acid (PABA) in the urine was significantly less than in the controls. In contrast, 328 of 353 controls and patients with non-pancreatic diseases (93 per cent) had PABA excretion within normal limits. The sensitivity and specificity of the Bentiromide-test observed in this study is sufficient to detect moderate to severe disturbances of pancreatic exocrine function. The PFT has proved to be an easy and reliable screening test for pancreatic exocrine function in ambulatory as well as in hospitalized patients.

Preliminary evaluation of a single-day tubeless test of pancreatic function

The test for pancreatic exocrine function using N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BTP test) does not require duodenal intubation, but misleadingly abnormal results often occur in patients with liver or bowel disease because the p-aminobenzoic acid (PABA) released by chymotrypsin hydrolysis of the peptide either is not conjugated or is malabsorbed. This study evaluated a modified BTP test, using a tracer dose of 14C-PABA to eliminate misleading results, to assess exocrine function from a single six-hour collection of urine. The test clearly distinguished all patients with pancreatic steatorrhoea from normal subjects and identified patients with less severe pancreatitis as often as did the Lundh test. Furthermore, in patients with bowel or liver disease the misleadingly abnormal results of the unmodified BTP test were eliminated by the modified test in all but one case. These findings suggest that the modified BTP test provides a practical alternative to conventional tests of pancreatic function that entail duodenal intubation.

Determination of protease-cleaved p-aminobenzoic acid (PABA) in serum after oral administration of N-benzoyl-L-tyrosyl-p-aminobenzoic acid (PABA-peptide) in children

A modification of the urine PABA tet published by Imondi et al. is described. Ninety minutes after oral administration of PABA peptide, PABA was determined in serum. The average concentration in healthy children was 0.42 +/- 0.055 mg per 100 ml. Up to that time we recovered in the urine 66.1 +/- 6.1% of the substance previously administered. In the children with cystic fibrosis of the pancreas (CF) serum PABA concentrations were less than 0.1 mg per 100 ml. The infants under 2 months old also had clearly low serum concentrations, on average 0.29 +/- 0.06 mg per 100 ml, whereas the PABA concentrations in the older babies lay within the range for the older children (0.40 +/- 0.07 mg%).

In vitro and in vivo analysis of the PABA test compared with the Lundh test--influence of intraluminal pH

Lundh test and PABA test results were compared in 50 patients. In the resulting correlation curve three areas of interest were differentiated: (1) an area with mean tryptic activity, found in the Lundh test, below 4 U/ml, where an abnormal PABA test result was also seen; (2) an intermediate area from 4 to 9 U/ml, where PABA test results may be found in discordance with the Lundh test; (3) the normal level, where PABA excretion was shown to be independent of intestinal chymotrypsin activity. In experiments in vitro on the kinetics of the hydrolysis of BTPABA by chymotrypsin the profound influence of the pH on Km and Vmax was shown. This influence of the pH explains why in the intermediate area of pancreatic dysfunction normal PABA test results were found in a number of cases. A higher mean pH level of the Lundh test aspirates was found for patients with a normal PABA test result than for patients with an abnormal PABA test.

The oral pancreatic function test with N-benzoyl-L-tyrosyl-p-aminobenzoic acid: acute toxicity and effects of renal function on this test

The oral pancreatic function test with N-benzoyl-L-tyrosyl-p-aminobenzoic acid was performed on 24 healthy test subjects, and its toxicity was examined. Eight patients with restricted renal function and known renal disease were also investigated. The pancreatic function test and the same procedure using free p-amino-benzoic acid were performed at 2-3-day intervals. During all the investigations with the pancreatic function test, no clinical side effects were observed. All parameters investigated at all the test times fell within the normal range. No toxicity of N-benzoyl-L-tyrosyl-p-amino-benzoic acid could be found. The excretion of p-aminobenzoic acid after administration of N-benzoyl-L-tyrosyl-p-aminobenzoic acid ws greatly reduced in all patients with restricted renal function. Four of eight patients also showed essentially no increase in excretion rate when free p-aminobenzoic acid was given instead of the peptide. It is therefore not possible to correct the pancreatic function test results in patients with renal insufficiency by calculating the ratio of p-aminobenzoic acid excretion after peptide intake to that after free p-aminobenzoic acid ingestion. Adequate renal function is therefore a prerequisite for the pancreatic function test.