Recovery Of P-aminobenzoic Acid Research Articles

Sensitivity and specificity of published strategies using urinary creatinine to identify incomplete 24-h urine collection

Objective Although urinary creatinine has been used to identify incomplete 24-h urine in numerous epidemiologic studies, information on its utility is limited. We examined the sensitivity and specificity of several strategies that use creatinine to identify incomplete urine using the p-aminobenzoic acid (PABA) check method as reference. Methods Subjects were 654 female Japanese dietetic students 18–22 y of age. A single 24-h urine sample was collected, with recording of the time of the start and end of the collection period and missing urine volume. Simultaneous administration of PABA was done to assess completeness. The sensitivity and specificity of five strategies derived from the literature that used creatinine to identify incomplete urine were calculated as the proportion of incomplete and complete urine correctly identified, respectively. Results A total of 7.6% of subjects was identified as having incomplete urine by PABA (PABA recovery <85%). This proportion significantly ( P < 0.0001) decreased (to 5.5%) after considering self-reported collection time and missing urine volume in the calculation of total urine volume. The sensitivity and specificity of the strategy of Knuimann et al. (incomplete urine = <0.7 of [mmol urinary creatinine × 113]/[21 × kilograms of body weight]) were 0.47 and 0.99, respectively. The corresponding values of other strategies were 0.11–0.22 and 0.57–1.00, respectively. Conclusion At least in well-motivated populations in which the proportion of incomplete urine is presumed to be small, the strategy of Knuimann et al. and consideration of the self-reported collection time and missing urine volume in the estimation of total volume may be useful.

The use of P-aminobenzoic acid and chromic oxide to confirm complete excreta collection in a carnivore, Felis silvestris catus

Complete excreta collection is a pre-requisite for several protocols in protein metabolism, and lack of confidence in achieving this may be increased when working with carnivores. Recovery of p-aminobenzoic acid (PABA) as a check for complete urine collection and chromic oxide for complete faeces collection were assessed in the cat. A single oral dose of PABA (4 mg/kg BW) was excreted more slowly than has been reported in the human (82% recovery at 6 h). A daily dose of PABA proved a useful method for confirming complete urine collection in the cat, and was 99% excreted in 72 h. Chromic oxide (500 mg/cat) was administered orally and recovery of chromium in the faeces was 90% after 96 h. A HPLC method for the analysis of PABA in cat urine was developed, and from the application of the techniques to a nitrogen balance study, it was concluded that PABA and chromic oxide are useful checks for complete excreta collection in the cat.

Quantification of benzocaine and its metabolites in channel catfish tissues and fluids by HPLC

Methods for extraction and gradient HPLC quantification were developed for benzocaine (BZ) and three of its metabolites to be used in conjunction with a reverse isotope technique. The metabolites were p-aminobenzoic acid (PABA), acetyl- p-aminobenzoic acid (AcPABA) and acetylbenzocaine (AcBZ). The matrixes studied were white muscle, red muscle, skin, liver, trunk kidney, head kidney, plasma and the bile of channel catfish. Analytes were validated for each of the compounds at 25 and 100 nmol per sample in the various tissues and fluids. The intraday variability (R.S.D.) was less than 13% in all tissues and fluids except for BZ in the liver. Recoveries varied from matrix to matrix for each analyte. The highest recoveries were obtained from plasma which ranged from 82.8–99.8% depending on the concentration. The average recovery of the compounds from tissues was between 50 and 78%, except for liver where the recovery of PABA and BZ was below 30%. Detection was by UV absorbance at 286 nm and the linear range was 2.5–15 nmol 100 ml −1 for all analytes. The method was selective; no interference peaks coeluted with the analytes.

Comparative effects of feeding a protease inhibitor-enriched potato protein concentrate and soy flour to rats

Rats were fed casein diets to which had been added a potato protein concentrate (PPC) at a level which provided trypsin- and chymotrypsin-inhibitor activities comparable to that present at the same level (10%) of protein derived from raw soy flour. Control groups consisted of the same diets in which the unheated PPC and raw soy flour were replaced by their heated counterparts in which over 90% of the inhibitor activities had been destroyed. After 5 weeks the following measurements were made: (1) growth, (2) PER, (3) pancreas weight, (4) protein digestibility, (5) a peptide test that reflects pancreatic function, and (6) enzyme activities (trypsin, chymotrypsin, amylase, and lipase) in the pancreas and small intestine. PPC was found to produce the same general pattern of effects as raw soy flour, namely, an inhibition of growth, a decrease in PER and protein digestibility, an increase in the size of the pancreas, an increase in the recovery of p-aminobenzoic acid in the peptide test, and a depletion of enzyme in the pancreas with concomitant increases in the intestines (except for trypsin). PPC was somewhat more effective than raw soy flour in causing an increase in trypsin and chymotrypsin activities in the faces.

Nonpancreatic hydrolysis of N-benzoyl-L-tyrosyl-p-aminobenzoic acid (PABA peptide) in the rat small intestine.

Factors affecting the intestinal hydrolysis of orally administered N-benzoyl-L-tyrosyl-p-aminobenzoic acid (PABA peptide) and urinary recovery of p-aminobenzoic acid have been studied in rats, after diversion of the pancreatic and biliary secretions. The exclusion of pancreatic secretions from the small intestine lowered, but did not completely abolish, the urinary recovery of PABA, whereas diversion of the bile had no significant effect. A particulate-bound enzyme capable of splitting PABA peptide was found to be present throughout the rat small intestine, and its activity remained unchanged in the absence of biliopancreatic secretions. The intestinal PABA peptide hydrolase could be solubilized with papain and Triton from a partially purified brush-border membrane fraction, and it eluted in gel filtration as a high-molecular-weight peak, well separated from the other known peptidases of the intestinal brush-border membrane.

Failure of p‐Aminobenzoic Acid Screening Test to Diagnose Pancreatic Insufficiency in Shwachman's Syndrome

SummaryThe 6‐h urine recovery of p‐aminobenzoic acid (PABA) following the administration of a standard dose of N‐benzoyl‐L‐tyrosyl‐p‐aminobenzoic acid (BTPABA) was performed in 13 control subjects and two siblings with Shwachman“s syndrome. The control subjects showed a recovery of 67 ± 12.1% (mean ± 1 SD) of the administered dose, consistent with previously reported values. Unexpectedly, the recovery of PABA in two siblings with Shwachman's syndrome was found to be 67 and 63%, respectively. The values are well within the normal range. In these siblings, fecal chymotrypsin activities were very low when measured with N‐acetyl‐L‐tyrosyl‐ethyl ester (ATEE) as substrate, but were normal when BTPABA was the substrate. The duodenal juice of the younger affected child following pancreozymin‐secretin stimulation showed very low chymotrypsin activity against ATEE, BTPABA, and N‐benzoyl‐L ‐tyrosyl‐ethyl ester. These findings suggest that there may be BTPABA‐splitting activity in the lower bowel of these siblings with Shwachman's syndrome. This activity might be that of enteric bacteria or of the intestinal mucosa.

Evaluation of postoperative exocrine pancreatic function using chymotrypsin labile peptide.

The assessment of exocrine pancreatic function by the oral administration of a chymotrypsin labile peptide N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA) has proved to be an easy and reliable test of exocrine pancreatic function. It has the additional advantage that it can be used to study exocrine pancreatic function in all operative cases, even after gastrointestinal reconstruction. The recovery of p-aminobenzoic acid (PABA) correlates significantly with parameters of the PZ/CCK secretin (PS) test. Following Billroth II gastrectomy, the recovery of PABA decreased to 39.8 +/- 3.2% two weeks after and to 45.4 +/- 4.5% one to two months after operation, significantly lower than the 80.6 +/- 3.4% in normal subjects. In cases of cancer of the head of the pancreas, the exocrine function was 44.0 +/- 3.7%, and decreased to 17.5 +/- 3.0% after total pancreatectomy. Thus, BT-PABA enables a pertinent evaluation of pancreatic function in postoperative patients with various types of gastrointestinal reconstruction and also in cases when the PS test cannot be feasibly used.

Failure of p-aminobenzoic acid screening test to diagnose pancreatic insufficiency in Shwachman's syndrome.

The 6-h urine recovery of p-aminobenzoic acid (PABA) following the administration of a standard dose of N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BTPABA) was performed in 13 control subjects and two siblings with Shwachman's syndrome. The control subjects showed a recovery of 67 +/- 12.1% (mean +/- 1 SD) of the administered dose, consistent with previously reported values. Unexpectedly, the recovery of PABA in two siblings with Shwachman's syndrome was found to be 67 and 63%, respectively. The values are well within the normal range. In these siblings, fecal chymotrypsin activities were very low when measured with N-acetyl-L-tyrosyl-ethyl ester (ATEE) as substrate, but were normal when BTPABA was the substrate. The duodenal juice of the younger affected child following pancreozymin-secretin stimulation showed very low chymotrypsin activity against ATEE, BTPABA, and N-benzoyl-L-tyrosyl-ethyl ester. These findings suggest that there may be BTPABA-splitting activity in the lower bowel of these siblings with Shwachman's syndrome. This activity might be that of enteric bacteria or of the intestinal mucosa.

Improved Diagnostic Accuracy of a Modified Oral Pancreatic Function Test

The oral pancreatic function test (PFT) depends upon urinary recovery of p-aminobenzoic acid (PABA) released by chymotrypsin hydrolysis of orally administered N-benzoyl-L-tyrosyl-p-aminobenzoid acid. The diagnostic value of the test is limited because falsely abnormal results frequently occur in patients with bowel or liver disease in whom PABA recovery is impaired by abnormal absorption or hepatic conjugation, even though pancreatic function is normal. To overcome this problem, we have modified the oral PFT to correct for impaired PABA absorption and conjugation. Results of the oral PFT have been compared with urinary recovery of an equivalent dose of free PABA in order to derive a PABA excretion index (PEI). When the modified oral PFT is used, the PEI clearly distinguished patients with pancreatic disease from normal subjects. In patients with small-bowel or liver disease and normal exocrine pancreatic function, the PEI results were similar to those of normal subjects, although a previous oral PFT had been falsey abnormal. The modified test can therefore distinguish abnormal results due to pancreatic disease from the falsely abnormal results found in liver and small-bowel disease.

PABA screening test for exocrine pancreatic function in infants and children.

P-Amino-benzoic acid (PABA) is split specifically by pancreatic chymotrypsin from the synthetic tripeptide N-benzoyl-L-tyrosyl-PABA. The urinary excretion of absorbed PABA serves as an index for exocrine pancreatic function. The peptide (0.015 g/kg) was administered orally to 20 controls (aged between 5 months and 16 years), 6 patients with exocrine pancreatic insufficiency caused by cystic fibrosis (CF), and 9 newborn infants. In the controls the mean 6-hour PABA recovery was 58.5% (+/- 11.2 SD). Recovery in patients with CF was lower (P less than 0.001) with no overlap. In newborn infants the mean 6-hour PABA recovery was 23.4 (+/- 17.7 SD); overlapping in 3 instances with the results in CF patients. This simple, noninvasive test thus appears promising and merits further investigation in younger infants, especially newborns.