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PubMed1982

Increase in the penetration of tracer compounds into the rat brain during 2-methyl-4-chlorophenoxyacetic acid (MCPA) intoxication.

The penetration of different intravenous tracer molecules such as 14C-labelled 2-methyl-4-chlorophenoxyacetic acid (14C-MCPA), 14C-p-aminobenzoic acid (14C-PABA), 14C-sucrose, 14C-antipyrine and iodinated (125I) human albumin (125I-HA) into the brain and cerebrospinal fluid (CSF) was studied in MCPA-intoxicated and control rats. Toxic subcutaneous doses of sodium salt of MCPA (200-500 mg/kg) increased highly the brain/plasma and CSF/plasma ratios of 14C-MCPA and 14C-PABA, as compared to the muscle/plasma ratio. Probenecid (200 mg/kg) did not affect the cerebral MCPA concentration in the intoxicated animals. The tissue/plasma ratios of 14C-sucrose, 14C-antipyrine and 125I-HA were also increased in the brain and CSF of intoxicated animals, but the increases were less pronounced than those of 14C-MCPA or 14C-PABA. The results indicate that MCPA intoxication caused a selective damage of the blood-brain barrier in the brain areas studied.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2005

Bacterially synthesized folate and supplemental folic acid are absorbed across the large intestine of piglets.

A large pool of folate exists in the large intestine of humans. Preliminary evidence, primarily in vitro, suggests that this folate may be bioavailable. The purpose of this study was to test the hypothesis that supplemental folic acid and bacterially synthesized folate are absorbed across the large intestine of piglets. The pig was used as an animal model because it resembles the human in terms of folate absorption, at least in the small intestine. A tracer of [3H]-folic acid or [3H]-para-aminobenzoic acid ([3H]-PABA), a precursor of bacterially synthesized folate, was injected into the cecum of 11-day-old piglets. Feces and urine were collected for 3 days. Thereafter, piglets were killed, and livers and kidneys harvested. [3H]-Folate was isolated from biological samples by affinity chromatography using immobilized milk folate binding proteins and counted using a scintillation counter. In piglets injected with [3H]-folic acid, the feces, liver, urine and kidneys accounted for 82.1%, 12.3%, 3.9% and 1.7% of recovered [3H]-folate, respectively. In piglets injected with [3H]-PABA, the amount of recovered bacterially synthesized folate in the feces, liver and urine was 85.1%, 0.4% and 14.6%, respectively. Twenty-three percent and 13% of tritium were recovered in samples examined (liver, kidney, fecal and urine) from piglets injected with [3H]-folic acid and [3H]-PABA, respectively. Using our estimates of [3H]-folic acid absorption and the total and percent monoglutamyl folate content of piglet feces, we predict that at least 18% of the dietary folate requirement for the piglet could be met by folate absorption across the large intestine.

4-Aminobenzoic Acid↗
PubMed1985

Determination of dopamine-3- and 4-O-sulphate in human plasma and urine by anion-exchange high-performance liquid chromatography with fluorimetric detection.

A high-performance liquid chromatographic (HPLC) method is reported for the determination of dopamine-3- and -4-O-sulphate isomers in human plasma and urine using an anion exchanger coupled with post-column hydrolysis and fluorimetric detection. Samples of plasma or urine are partially purified on Dowex 1 and Dowex 50 columns and separated using HPLC. These compounds are then hydrolysed and determined automatically by the p-aminobenzoic acid method in a continuous-flow reaction system. As the p-aminobenzoic acid method is very specific for dopamine, it is also possible to determine the isomers by injecting 5-20 microliter of urine or 100-200 microliter of deproteinized plasma directly into the HPLC system without clean-up. The detection limit of the method for both isomers is 0.3 pmol. In normal subjects, the plasma levels of dopamine-3- and -4-O-sulphate are 26.5 (S.D. 11.1) and 2.68 (S.D. 0.34) pmol/ml, and their urinary excretion rates are 1.73 (S.D. 0.56) and 0.27 (S.D. 0.04) nmol/min, respectively. Thus the two isomers are present in both plasma and urine and their urinary excretions reflect directly their plasma levels.

Chromatography, High Pressure Liquid↗
PubMed2000

Effects of carmustine and lomustine on arylamine N-acetyltransferase activity and 2-aminofluorene-DNA adducts in rat glial tumor cells.

Carmustine and lomustine are nitrosourea antitumor chemotherapeutic agents which were used to determine whether or not they could affect arylamine N-acetyltransferase (NAT) activity and DNA-2-aminofluorene adducts in rat glial tumor cell line (C6 glioma). The NAT activity was measured by high preformance liquid chromatography (HPLC) assaying for the amounts of N-acetyl-2-aminofluorene (AAF) and N-acetyl-p-aminobenzoic acid (N-Ac-PABA) and remaining 2-aminofluorene (AF) and p-aminobenzoic acid (PABA). The results indicate that NAT activity in glial tumor cell cytosols and intact tumor cells were decreased by carmustine and lomustine in a dose-dependent manner. The apparent values of Km and Vmax of NAT from rat glial tumor cell also decreased after co-treatment of carmustine and lomustine in both examined cytosols and intact cells. Following exposure of glial tumor cells to the various concentrations of AF with or without co-treatment with carmustine and lomustine, DNA-AF adducts were determined by using gamma-[32p]-dATP and HPLC. The DNA-AF adducts in rat glial tumor cells were decreased by co-treatment with carmustine and lomustine. This report is the first demonstration to show carmustine and lomustine did inhibit rat glial tumor cells NAT activity and DNA-AF adduct formation.

Animals↗
PubMedDate not supplied

Curcumin decreases the DNA adduct formation, arylamines N-acetyltransferase activity and gene expression in human colon tumor cells (colo 205).

The effects of curcumin on the N-acetyltransferase (NAT) activity, AF-DNA adduct formation and NAT gene expression were examined using the human colon tumor cell line (colo 205). Various concentrations of curcumin were added to the cytosols or to the medium of human colon tumor cells. The NAT activity was determined by high performance liquid chromatography assaying for the amounts of acetylated 2-aminofluorene (AAF) and p-aminobenzoic acid (N-Ac-PABA) and nonacetylated 2-aminofluorene (AF) and p-aminobenzoic acid (PABA). The NAT activity in the human colon tumor cells and cytosols was suppressed by curcumin in a dose-dependent manner. The results demonstrated that gene expression (NAT1 mRNA) in human colon tumor cells was inhibited by curcumin. The apparent values of Km and Vmax of NAT of human colon tumor cells were also decreased by curcumin in cytosols. Curcumin may act as a noncompetitive inhibitor. After the incubation of human colon tumor cells with AF with or without curcumin cotreatment, the cells were recovered and DNA was prepared, hydrolyzed to nucleotides, the adducted nucleotides were extracted into butanol and AF-DNA adducts analyzed by HPLC. The results also demonstrated that when curcumin was added to the media a decrease in AF-DNA adduct formation was seen in the human colon tumor cells. The finding of AF-DNA adduct formation in cultured human colon tumor cells suggests the usefulness of cultured cells for assessing arylamine-induced DNA damage.

Antineoplastic Agents↗
PubMed1985

UV-induced photoproducts of para-aminobenzoid acid.

Cis- and trans- 4,4'-azodibenzoic acid (AZBA), two photoproducts of para-aminobenzoic acid (PABA), formed by the action of 313 nm light, have been characterized on the basis of UV and mass spectral data. The relative dose of UV light required for azodibenzoic acid formation is comparable to that obtained from a day of sunbathing. The same type of photochemical reaction could lead to the formation of PABA-protein conjugates. These photoproducts may be responsible for the known photosensitizing properties of PABA and perhaps its cytotoxic and mutagenic effects.

4-Aminobenzoic Acid↗
PubMed1991

Follicles play an important role in percutaneous absorption.

The relative importance of stratum corneum and follicles in percutaneous absorption is not fully understood. In order to quantitatively investigate the importance of the transappendageal route, we have previously developed a model of skin without follicles regrown dorsally on the hairless rat. Percutaneous absorption was compared, using a diffusion cell, in appendage-free skin relative to normal skin, and a predominant role of follicles for in vitro diffusion of [3H]hydrocortisone was noted. Results presented here of in vitro diffusion of tritiated hydrocortisone, niflumic acid, caffeine, and p-aminobenzoic acid, applied in acetone, confirm that appendageal diffusion is the major pathway in hairless rat skin. In the absence of follicles, the steady-state flux and the amounts diffusing in 24 or 48 h are 2-4 times lower than in normal skin. These results were confirmed in a second model in which diffusion of [3H]hydrocortisone was studied on skin samples taken one day after birth, at which time rat skin is still devoid of follicles, relative to five-day postnatal skin samples, in which follicles are fully developed. The steady-state flux and the total diffusion in 24 h were fivefold lower in follicle-free skin. These results support the view that follicles may have a far greater importance in percutaneous absorption than is generally assumed.

4-Aminobenzoic Acid↗
PubMed1987

NMR investigation of the influence of procaine and its metabolites on the water exchange through human erythrocyte membranes.

The effect of procaine hydrochloride and its metabolites on the diffusional water exchange through erythrocyte membranes was investigated at 37 degrees C and at concentrations ranging between 5 X 10(-5) M and 5 X 10(-1) M by using the NMR manganese doping method. Procaine hydrochloride and 2-diethylaminoethanol have a moderate stimulating effect on the water exchange, of up to 20% at concentrations ranging between 10(-3) and 10(-2) M, while an increasing inhibitory effect was found at higher concentrations. The p-aminobenzoic acid has no effect on the water exchange up to 10(-2) M and, at higher concentrations, and apparent decreasing inhibition was noticed which is thought to be an artefact due to the uptake of Mn2+ by the cells. The temperature dependence studies suggest that procaine HCl enhances the uptake of Mn2+ by the cells. An opposite effect was found for rigid erythrocytes. The p-aminobenzoic acid and 2-diethylaminoethanol appeared to be more effective than procaine hydrochloride in increasing the uptake of Mn2+.

4-Aminobenzoic Acid↗
PubMed1975

A study of chemical light screening agents.

In a group of 104 non-photosensitive subjects and seventy-eight suffering from a variety of photodermatoses, the most effective protective preparation against irradiation by short UV sunburn wavelengths (smaller than 320 nm) was found to be a mixture of 5% para-aminobenzoic acid and 2.5% of the ester amyl dimethylaminobenzoate in 70% ethanol with para-aminobenzoic acid being usually more effective than the ester, and mexenone the least effective individually. The protective capacity was found to be reduced by showering but not by exercise. The addition of glycerol to the formulations did not affect their protective capacity although the addition of propylene glycol did increase the protection obtained.

Aminobenzoates↗
PubMed1988

Nutritional requirements of Methanomicrobium mobile.

A defined medium was developed for Methanomicrobium mobile BP. M. mobile required acetate for growth; the optimal concentration was 30 mM. Other requirements and their optimal concentrations included isobutyrate (0.65 mM), isovalerate (0.73 mM), and 2-methylbutyrate (1.5 mM). The appropriate branched-chain amino acids did not substitute for these branched-chain fatty acids. M. mobile required tryptophan at an optimal concentration of 24 microM. Indole substituted for tryptophan, but the possible precursor compounds shikimic acid and anthranilic acid and the degradation compound skatole did not. Vitamin requirements and their optimal concentrations included pyridoxine (0.49 microM), thiamine (0.15 microM), biotin (0.04 microM), and vitamin B12 (0.04 microM); p-aminobenzoic acid (0.18 microM) was required for optimal growth, but folic acid did not replace p-aminobenzoic acid. M. mobile required an unidentified growth factor found in ruminal fluid or extracts of Methanobacterium thermoautotrophicum for growth. M. mobile has a complex nutrition compared with that of other methanogens, but not an unusual nutrition in the context of organisms from the ruminal ecosystem.

Acetates↗
PubMed1993

Polymorphic N-acetylation of 2-aminofluorene by cell-free colon extracts from inbred mice.

The increased risk of rapid acetylator humans for the development of colorectal cancer has created interest in experimental animal models to study the relationship of N-acetyltransferase phenotype to colon cancer. Colon cytosols from inbred mouse lines were assayed for the ability to N-acetylate 2-aminofluorene to determine if the mouse model of the N-acetyltransferase polymorphism could be used to study this relationship. The results indicate that the colon acetylcoenzyme A: 2-aminofluorene-N-acetyltransferase activity parallels that of the liver. Colon activity from slow acetylator (A and B6.A) mouse lines is significantly lower than that of rapid acetylator (B6, B6.D, and A.B6) lines. p-Aminobenzoic acid N-acetyltransferase activity also differed between colon cytosols from rapid and slow acetylator strains. Isoniazid acetylation in colon and in liver did not differ between phenotypes. Northern blot analysis demonstrated the presence of mRNA for both NAT-1 and NAT-2 in mouse colon as well as in mouse liver. These results indicate that the N-acetyltransferase polymorphism is expressed in mouse colon when 2-aminofluorene or p-aminobenzoic acid is used as substrate and therefore the mouse may be a model for study of the effect of acetylator phenotype on development of colorectal cancer in humans.

4-Aminobenzoic Acid↗
PubMedDate not supplied

Serum lipase, isoamylase and pancreatic function test (PFT) in juvenile-onset insulin-dependent diabetes mellitus.

Significantly decreased activity of pancreatic isoamylase in serum was found in a group of 51 juvenile-onset insulin-dependent diabetics as compared to healthy subjects (p less than 0.005). No significant changes were observed for urinary p-aminobenzoic acid excretion in 20 of the juvenile-onset diabetics in whom the NBT-PABA test was performed, even though 25% of the values were below the normal limit. A highly significant decrease of serum lipase activity was found in juvenile-onset diabetics as compared to controls (p less than 0.001). No significant correlation was found in juvenile-onset diabetics between serum pancreatic isoamylase and lipase or marker of chymotrypsin activity expressed as the amount of p-aminobenzoic acid excreted into urine. The NBT-PABA test appears to be of small importance in the evaluation of changes of the exocrine pancreas in insulin-dependent diabetes mellitus. However, simultaneous evaluation of serum pancreatic isoamylase and lipase activities justified the suspicion of pancreatic damage in 50% of the patients tested.

4-Aminobenzoic Acid↗
PubMed1980

Simultaneous evaluation of pancreatic exocrine function and intestinal absorptive function in dogs with chronic diarrhea.

The N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA):xylose test was evaluated in 5 clinically normal dogs, 5 dogs with pancreatic exocrine insufficiency (PEI), and 7 dogs with intestinal malabsorption. A solution of BT-PABA (1 g/100 ml) and d-xylose (10 g/100 ml) was given orally (5 ml/kg of body weight) to dogs in each group. Plasma p-aminobenzoic acid (PABA) curves were decreased in dogs with PEI and intestinal malabsorption (P < 0.05) but were the lowest in dogs with PEI, compared with clinically normal dogs. Xylose values in dogs with malabsorption were decreased (P < 0.05), compared with clinically normal dogs. Dogs with PEI had plasma xylose values that were intermediate to values in clinically normal dogs and dogs with intestinal malabsorption. Results of BT-PABA:xylose testing were compared with results of sodium PABA:xylose testing, to determine whether decreased PABA values obtained by the BT-PABA:xylose test were caused by free PABA malabsorption or by maldigestion of BT-PABA. The sodium PABA:xylose test was performed in dogs from each group by oral administration of a solution (5 ml/kg) of sodium PABA (0.372 g/100 ml) and d-xylose (10.0 g/100 ml). Plasma PABA values obtained by the sodium PABA:xylose test were similar in each group. Thus, different PABA values obtained by the BT-PABA:xylose test were not caused by PABA malabsorption. Xylose values were similar to values obtained by the BT-PABA:xylose test. It was concluded that: (1) the BT-PABA:xylose test is a practical test for detecting maldigestion or malabsorption in the dog; (2) dogs with intestinal malabsorption may have functional PEI; and (3) decreased PABA plasma values obtained by BT-PABA:xylose testing are not caused by malabsorption of free PABA.

4-Aminobenzoic Acid↗
PubMed1975

Hepatic and extrahepatic N-acetyltransferase. Perinatal development using a new radioassay.

We report a sensitive and rapid radioassay method for p-aminobenzoic acid N-acetyltransferase. The principle of this assay involves acetylation of p-aminobenzoic acid with [1-14C] labeled acetyl coenzyme A and direct extraction of enzymically formed radioactive p-acetamidobenzoic acid into nonaqueous scintillation fluid. Using this radiometric assay, hepatic and extrahepatic tissue distributions from rat and rabbit were studied. Rabbit blastocyst and endometrial N-acetyltransferase specific activities were equivalent to hepatic activities. Perinatal development studies in rats and rabbits revealed that fetal and neonatal animals are capable of N-acetylation. Rat liver developmental studies exhibited two peaks of activity with the first peak occurring in the late fetus followed by a second peak 3 days after birth. Rabbit fetal and neonatal enzyme activity increased to adult levels by the second week after birth in liver and gut, however, lung showed a different developmental pattern. These studies demonstrate that fetal extrahepatic tissues, like adult tissues, play an important role in N-acetylation.

Acetyltransferases↗
PubMed1999

Effects of garlic components diallyl sulfide and diallyl disulfide on arylamine N-acetyltransferase activity in human bladder tumor cells.

Diallyl sulfide (DAS) and diallyl disulfide (DADS) were used to determine viability and inhibition of arylamine N-acetyltransferase (NAT) activity in human bladder tumor cells. The NAT activity was measured by high performance liquid chromatography assaying for the amounts of N-acetyl-2-aminofluorene (2-AAF) and N-acetyl-p-aminobenzoic acid (N-Ac-PABA) and remaining 2-aminofluorene (2-AF) and p-aminobenzoic acid (PABA). The viability, NAT activity and 2-AAF-DNA adduct formation in human bladder tumor cells was inhibited by DAS and DADS in a dose-dependent manner, i.e. the higher the concentration of DAS and DADS, the higher the inhibition of NAT activity and cell death. The data also indicated that DAS and DADS decrease the apparent values of Km and Vmax from human bladder tumor cells in both systems examined. This report is the first demonstration to show garlic components did affect human bladder tumor cell NAT activity.

Allyl Compounds↗
PubMed2000

The N-acetylation of arsanilic acid In vitro by mammalian enzymes.

The N-acetylation of arsanilic acid was assayed in vitro by modifying a literature method for acetylation of p-aminobenzoic acid. Conditions included final concentrations of 1.0 mM dithiothreitol, 1.0 mM EDTA, 0.45 mM acetyl coenzyme A, an acetyl coenzyme A regenerating system using bacterial phosphotransacetylase and acetyl phosphate, 5.0 mM arsanilate substrate, and 25 mM sodium/potassium phosphate buffer, pH 7.4, in a total volume of 0.5 ml. Incubation was at 37 degrees C, with 0.5- to 2-mg N-acetyltransferase enzyme protein from a preparation of guinea pig liver. The reaction was terminated by heat precipitation. The resulting supernatant was put through a 4 mm 0.45 microm polysulfone membrane syringe filter. The filtrate could then be injected directly onto the HPLC. With arsanilic acid as substrate, the product N-acetylarsanilic acid (NAA) was identified by its retention time (33 min) in the HPLC system of the laboratory. The 33-min fraction collected from the HPLC was scanned and gave the characteristic UV spectrum of NAA, with peaks at 203 and 256 nm. In addition, the product comigrated in the HPLC system with standard NAA. Under comparable assay conditions, the N-acetylation of arsanilate by the guinea pig enzyme preparation is about 24% the rate of that of the model substrate p-aminobenzoic acid. Typical activity for arsanilate acetylation was 0.5 nmol/min/mg enzyme protein. Using the same assay system and HPLC detection method, the supernatant from bacterial lysates containing recombinant human N-acetyltransferase 1 exhibited acetylation activity toward arsanilate of 720 nmol/min/mg enzyme protein.

Acetylation↗
PubMed1994

Arylamine N-acetyltransferase activity of the human placenta.

The fetus is exposed to almost all of the substances found in the maternal circulation whether nutrients or foreign chemicals ("xenobiotics"). The main route of exposure is the placenta. The placenta is metabolically active toward xenobiotics and the nature of the compounds reaching the fetal circulation will, in part, depend on placental biotransformation reactions. Arylamine N-acetyltransferase (NAT) catalyzes the acetyl CoA-dependent N-acetylation of primary arylamine and hydrazine substrates such as sulfamethazine, isoniazid, p-aminobenzoic acid as well as arylamine carcinogens such as 2-aminofluorene and benzidine. NAT activity is multigenically determined and can be attributed to two independently expressed proteins: NAT1 and NAT2. The acetylation capacity of the human placenta has not been investigated extensively. In the current study we identified and characterized the NAT activity of human term placenta. The kinetic data show that the activity of NAT in human placenta predominantly reflects the NAT1 enzyme. The apparent affinity (19.1 +/- 0.97 microM; mean +/- S.E.M., n = 22) and maximal velocity (3.84 +/- 0.32 nmol/min/mg; mean +/- S.E.M., n = 22) of p-aminobenzoic acid N-acetylation are similar to those measured in other tissues such as liver, blood lymphocytes, neutrophils and monocytes. In addition, there is evidence of NAT2 activity in some of the placental samples assayed, although the contribution of a small amount of NAT2 activity to the overall acetylation capacity of the placenta is likely to be small.

4-Aminobenzoic Acid↗
PubMed1989

Contact photoallergy testing of sunscreens in guinea pigs.

The potential of 3 sunscreens (p-aminobenzoic acid, 4-isopropyldibenzoylmethane and homosalate) and 2 known human photoallergens (musk ambrette and tetrachlorosalicylanilide) to cause photoallergy, phototoxicity, and/or contact sensitization was determined using a guinea pig photoallergy model, as previously described by Harber and associates. The model was slightly modified by employing 6 exposures over 2 weeks and using Hill Top Chambers for application of the test material. Contact photoallergy was detected in guinea pigs treated with musk ambrette or tetrachlorosalicylanilide (TCSA), although with TCSA, a lower incidence of contact sensitivity and phototoxicity was also detected. The results of studies conducted with sunscreens showed that p-aminobenzoic acid was photoallergenic, whereas homosalate and 4-isopropyl-dibenzoylmethane (Eusolex 8020) were not. However, contact sensitization, and to a lesser degree primary irritation, was detected with Eusolex 8020 at the concentrations employed in this study. The results of these studies suggest that this guinea pig model is a suitable model for assessing the photoallergic potential of various compounds, including the sunscreens tested in this study.

4-Aminobenzoic Acid↗