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P C Hirom

Publications and source records attributed to P C Hirom.

At least 19 recordsLinked to original sources
PubMed1991

SF-B that binds to a negative element in glutathione transferase P gene is similar or identical to trans-activator LAP/IL6-DBP.

We have previously identified a silencer (negative enhancer) in glutathione transferase P (GST-P) gene which is strongly and specifically induced during hepatocarcinogenesis of the rat. At least three trans-acting factors bind to multiple cis-elements located in this silencer. One of these factors, SF-B (Silencer Factor B) specifically binds to GPS1 (GST-P Silencer 1) and has been cloned by a Southwestern protocol. Analysis of DNA and deduced amino acid sequence reveals that SF-B clone is most likely identical to an IL-6 inducible trans-activator LAP/IL6-DBP. Binding efficiency of SF-B to GPS1 is indistinguishable from that to IL6-responsive element found in C-reactive protein gene. The possibility that SF-B/LAP/IL6-DBP functions as a dual positive and negative regulator is discussed.

Amino Acid Sequence↗
PubMed1988

Glutathione transferase activities of cultured human lymphocytes.

We have detected glutathione transferase (GST) activity towards 1-chloro-2,4-dinitrobenzene (CDNB) and benzo[a]-pyrene 4,5-oxide (BPO) in freshly isolated peripheral lymphocytes, phytohaemagglutinin (PHA)-stimulated lymphocytes, interleukin-2 (IL-2)-dependent T-cells and lymphoblastoid B-cell lines. The detection of conjugating activity with BPO implies the expression of a neutral, 'mu-like' GST form by both resting and cultured lymphocytes. In a sample of 12 unrelated individuals, BPO conjugating activity of freshly isolated lymphocytes showed a polymorphic distribution. In comparison with freshly isolated cells, BPO activity was increased 2- to 5-fold in IL-2-dependent T-cells and 4- to 10-fold in B-cell lines. The CDNB activity of T-cells was not significantly different to that of freshly isolated cells (P greater than 0.05) but activity in B-cell lines showed a significant increase (P less than 0.01). These data indicate that measurement of BPO activity in freshly isolated lymphocytes may allow the study of the human GST-mu polymorphism. However, IL-2-dependent culture of T-cells or viral immortalization of resting lymphocytes appears to cause the activation or induction of a GST form or forms which conjugate BPO efficiently. In the T-cells this effect may be mediated through addition of IL-2 to the culture since PHA treatment alone did not elevate activity.

Benzopyrenes↗
PubMed1986

Reactive intermediates from 3-hydroxybenzo[a]pyrene and its glucuronide.

3-Hydroxybenzo[a]pyrene (3-OH-BaP) is oxidized by the horseradish peroxidase/H2O2 system to benzo[a]pyrene-3,6-quinone. In the presence of N-acetylcysteine one other product is also formed. This was identified by its chemical, and u.v., mass and n.m.r. spectral properties as 6-(H-acetyl-cystein-S-yl)-3-hydroxybenzo[a]pyrene (6-NAc-cys-3-OH-BaP). Replacement of the N-acetylcysteine by glutathione leads to the formation of a 3-OH-BaP-glutathione adduct. Enzymic hydrolysis of benzo[a]pyrene-3-glucuronide in the presence of N-acetylcysteine yields, in addition to 3-OH-BaP, a product which co-chromatographs with 6-NAc-cys-3-OH-BaP and has identical chemical and spectral characteristics.

Acetylcysteine↗
PubMed1985

Secondary metabolites of benzo[a]pyrene: 3-hydroxy-trans-7,8-dihydro-7,8-dihydroxybenzo[a]pyrene, a biliary metabolite of 3-hydroxybenzo[a]pyrene in the rat.

Rats administered 3-hydroxybenzo[a]pyrene (50 mg/kg, i.p.), excrete via the bile metabolites which, after treatment with beta-glucuronidase and aryl sulphatase, yield, in addition to 3-hydroxybenzo[a]pyrene, 3-hydroxy-trans-7,8-dihydro-7,8-dihydroxybenzo[a]pyrene (3-OH-BP-7,8-diol) and a minor, highly labile, metabolite tentatively identified as 3,5-dihydroxybenzo[a]pyrene. These novel metabolites are readily isolated in a pure state via preparative layer chromatography. The structure of the 3-OH-BP-7,8-diol was revealed by its u.v., proton magnetic resonance and mass spectral properties. Its hydroxyl functions are in a predominantly quasi-diequatorial conformation.

Animals↗
PubMed1985

Metabolism and enterohepatic circulation of benzo(a)pyrene-4,5-epoxide in the rat.

After i.v. administration of 3H-benzo(a)pyrene-4,5-epoxide (32.5 mumol/kg) to rats, 76% of the 3H appeared in bile within 3 h. The glutathione conjugate of benzo(a)pyrene-4,5-epoxide was the major biliary metabolite (33% of dose), together with a glucuronic acid conjugate of benzo(a)pyrene-4,5-diol (18%) and an unidentified metabolite (10%). The glutathione and glucuronic acid conjugates both undergo extensive enterohepatic circulation. Thus, following the intraduodenal administration of the 3H-labelled conjugates, 26% of the radioactivity was excreted in the bile after 24 h in the case of the glutathione derivative, and 40% in the case of the glucuronide. The benzo(a)pyrene-4,5-diol glucuronide, on enterohepatic circulation, appears in the bile in the same form as the conjugate administered with no evidence of further metabolism of the polycyclic hydrocarbon moiety. The glutathione conjugate of benzo(a)pyrene-4,5-epoxide, on recirculation, is reexcreted in bile as one unidentified metabolite, which is susceptible to the action of arylsulphatase.

Animals↗
PubMed1982

Metabolism and excretion of benzo[a]pyrene in the rabbit.

1. Following i.v. administration of [14C]benzo[a]pyrene (3 mumol/kg) to rabbits, 30% of the 14C dose appeared in bile and 12% in urine, within six hours. 2. Biliary and urinary metabolites were mainly conjugated; less than 12% of the 14C was extractable with ethyl acetate, but after treatment with beta-glucuronidase or aryl sulphatase 30-40% became extractable. 3. H.p.l.c. analysis of the extracts indicated that the major non-polar metabolite was benzo[a]pyrene, 9,10-diol (18% of 14C in bile and 24% of 14C in urine, mainly conjugated with glucuronic acid). Smaller amounts of the 4,5-diol, the 3,6-quinone, and the 9-hydroxy- and 3-hydroxybenzo[a]pyrene were also found in bile (total less than 10%), together with 9-hydroxybenzo[a]pyrene and two unknown metabolites (X and Y) in urine (total less than 4%). 4. The proximate carcinogen, the 7,8-diol, was not detected in any extract. 5. After intraduodenal administration of biliary metabolites of [14C]benzo[a]pyrene (approx. 0 X 3 mumol), 14C was excreted in the bile (21% dose) and urine (14%) within 23 h, indicating that metabolites can undergo enterohepatic circulation in the rabbit.

Animals↗
PubMed1981

Biliary excretion, systemic availability and reactivity of metabolites following intraportal infusion of [3H]benzo[a]pyrene in the rat.

Following the intraportal infusion of [3H]benzo[a]pyrene (BP) at two dose levels (5 and 0.125 mumol/kg) in the rat, metabolites were excreted via the bile and were released into the hepatic venous blood. At each dose level, a significant portion (approx. 15-18%) of biliary metabolites was directly extractable with ethyl acetate and a total of approx. 24-32% became extractable after incubation of bile with beta-glucuronidase. More than 65% and 70% of the 3H in blood and liver, respectively, was directly extractable with ethyl acetate. The h.p.l.c. profile of extracted metabolites was found to differ at the two dose levels studied. The binding of reactive metabolites to hepatic protein and DNa was measured at four dose levels of [3H]BP. The possible availability of hepatic-derived metabolites to extra-hepatic sites is discussed.

Animals↗
PubMed1980

Enterohepatic recycling of phenolphthalein, morphine, lysergic acid diethylamide (LSD) and diphenylacetic acid in the rat. Hydrolysis of glucuronic acid conjugates in the gut lumen.

1. Biliary elimination in female Wistar albino rats 3 h after i.p. injection of [3H]phenolphthalein, [3H]morphine, 14C-LSD and [14C]diphenylacetic acid was 90%, 45%, 75% and 57% respectively, predominantly as glucuronides. 2. Infusion of 3 h bile from the previous experiments into the duodena of bile-duct-cannulated animals demonstrated enterohepatic circulation, amounting in 24 h to 85%, 41%, 28% and 66% of the infused doses of the conjugates of phenolphthalein, morphine, LSD and diphenylacetic acid respectively. 3. Pretreatment with antibiotics to suppress intestinal microflora decreased this enterohepatic recirculation to 22%, 8.6% and 21% in 24 h for phenolphthalein, morphine and diphenylacetic acid glucuronides respectively. Antibiotic pretreatment did not influence the absorption and re-excretion of infused doses of the free aglycones, thus demonstrating the importance of bacterial beta-glucuronidase hydrolysis of the biliary conjugates. 4. The extent of intestinal absorption of the aglycones after bacterial beta-glucuronidase hydrolysis of the conjugates is related to their lipid-solubility as estimated by octan-1-ol:0.1 M phosphate buffer partition ratios (P-values). 5. The persistence of compounds in the enterohepatic circulation is determined by the faecal and urinary elimination of the circulating compounds. Faecal elimination is governed by the extent of intestinal absorption of the circulating compounds, which is influenced by the efficacy of intestinal hydrolysis of the conjugates and the relative lipophilicity of the aglycones released.

Animals↗
PubMed1978

The influence of dose on the pattern of conjugation of phenol and 1-naphthol in non-human primates.

1. The pattern of conjugation of phenol and 1-naphthol was investigated in several primates; three Old World species (rhesus, cynomolgus, patas monkeys), two New World species (capuchin, tamarin), and two prosimians (bushbaby, tree shrew). 2. Following intra-muscular phenol or 1-naphthol (10 mg/kg), sulphation was the major conjugation in the Old World monkeys and prosimians, whereas glucuronidation predominated in the New World species. 3. In rhesus and cynomolgus monkeys, sulphation decreased as dose increased, but remained the major conjugation with both substrates at dose levels of 0.01 to 25 mg/kg. 4. In the capuchin, the conjugation pattern of phenol changed markedly as dose increased; at 0.01 and 1 mg/kg sulphation was the major conjugation, whereas at 10 and 25 mg/kg glucuronidation predominated. With 1-naphthol only small amounts of sulphate were excreted; glucuronic acid conjugation was the major metabolism at all four dose levels. 5. The importance of considering both substrate and dose when making inter-species comparisons, particularly with man, is discussed.

Animals↗
PubMed1976

A study of the physicochemical interactions between biliary lipids and chlorpromazine hydrochloride. Bile-salt precipitation as a mechanism of phenothiazine-induced bile secretory failure.

Since chlorpromazine hydrochloride [2-chloro-10-(3-dimethylaminopropyl)-phenothiazine hydrochloride] is commonly implicated in causing bile-secretory failure in man and is secreted into bile, we have studied the physicochemical interactions of the drug with the major components of bile in vitro. Chlorpromazine hydrochloride molecules are amphiphilic by virtue of possessing a polar tertiary amine group linked by a short paraffin chain to a tricyclic hydrophobic part. At pH values below the apparent pK (pK'a 7.4) the molecules are water-soluble cationic detergents. We show that bile salts in concentrations above their critical micellar concentrations are precipitated from solution by chlorpromazine hydrochloride as insoluble 1:1 salt complexes. In the case of mixed bile-salt/phosphatidylcholine micellar solutions, however, the degree of precipitation is inhibited by the phospholipid in proportion to its mole fraction. With increases in the concentration of chlorpromazine hydrochloride or bile salt, micellar solubilization of the precipitated complexes results. Sonicated dispersions of the negatively charged phospholipid phosphatidylserine were also precipitated, but dispersions of the zwitterionic phospholipid phosphatidylcholine were not. Chlorpromazine hydrochloride efficiently solubilized these membrane phospholipids as mixed micellar solutions when the drug:phospholipid molar ratio reached 4:1. Polarizing-microscopy and X-ray-diffraction studies revealed that the precipitated complexes were amorphous and potentiometric studies confirmed the presence of a salt bond. Some dissociation of the complex occurred in the case of the most polar bile salt (Ks 0.365). As canalicular bile-salt secretion determines much of bile-water flow, we propose that complexing and precipitation of bile salts by chlorpromazine hydrochloride and its metabolites may be physicochemically related to the reversible bile-secretory failure produced by this drug.

Animals↗
PubMed1976

Bile and urine as complementary pathways for the excretion of foreign organic compounds.

1. The urinary and biliary excretion in the rat of 30 aromatic compounds with mol. wt. of 100-850, and largely excreted unchanged, has been studied. 2. These compounds fall into three groups as regards their pattern of elimination, which is related to mol. wt: group 1, with mol. wt. less than 350 and the major route of elimination the urine. When urinary excretion is prevented by ligating the renal pedicles the biliary excretion remains low. group 2, with mol, wt. of 450-850 which are excreted predominantly in bile. Even when the bile duct is obstructed, only small amounts of these compounds are found in urine. group 3, with mol. wt. of 350-450, which are eliminated extensively in both urine and bile. When one of these routes is blocked excretion by the other increases. 3. These studies emphasize the interrelationship of urine and bile as excretory routes for organic compounds. Urine and bile are complementary pathways; the extent of urinary excretion is greatest for the compounds of lowest mol. wt. and tends to decrease as mol. wt. increases and biliary excretion becomes more extensive.

Animals↗