Doping in sport—1. Excretion of 19-norandrosterone by healthy women, including those using contraceptives containing norethisterone

19-Norandrosterone (19-NA) is the principal urinary metabolite of the anabolic steroid nandrolone and its prohormones. The administration of these 19-nor androgens is prohibited in sport by the World Anti-Doping Agency (WADA) but, even so, adverse findings for 19-NA continue to be commonly reported. Little is known about the urinary concentrations of 19-NA that can occur in women who are not using anabolic steroids, including those using oral contraceptives containing the 19-nor progestogen norethisterone. In 2004, WADA lowered the reporting threshold for 19-NA for females from 5 to 2 ng/mL. The lack of any substantial data on 19-NA excretion in women prompted this large-scale investigation. In this investigation, single untimed urines collected from 1202 female volunteers, 38 of whom were taking norethisterone containing contraceptives, were analysed for 19-NA. None of the women was a competitive athlete and pregnancy had been excluded by a urinary test for human chorionic gonadotropin (hCG). Only one sample exceeded the 19-NA reporting threshold having a concentration of 4.1 ng/mL. This sample was from a user of a norethisterone-containing contraceptive.     

Biliary and urinary excretion of peptide leukotrienes in the domestic pig

The metabolism of leukotriene (LT)C4 and its major routes of elimination in vivo have been studied in four anesthetized domestic pigs administered intravenous [3H]-LTC4 (0.5 microCi/kg). The kinetic profile of LTC4 in the blood was followed for 60 min after administration while the biliary and urinary excretion of LTC4 and its metabolites were determined over a 120 min interval. The total recovery of radioactivity in bile and urine was 45% +/- 1 (n = 3) and 18% (n = 2) respectively. Examination of the radioactive metabolites in bile showed LTD4 (44% of biliary content) and LTE4 (21% of biliary content) as the major identified lipoxygenase products at t 1/2 (27 min). The only identified cysteinyl leukotriene observed in the urine was LTE4 (13% of urinary content). In both bile and urine substantial amounts of radioactivity were detected at the solvent front of the reverse phase chromatographic system indicating the presence of additional unidentified metabolites. We suggest that measurement of metabolites using these sampling methods may be useful for the detection and measurement of peptide leukotriene production in vivo.     

Biliary and urinary excretion of peptide leukotrienes in the domestic pig

The metabolism of leukotriene (LT)C₄ and its major routes of elimination have been studied in four anesthetized domestic pigs administered intravenous [³H]-LTC₄ (0.5 μCi/kg). The kinetic profile of LTC₄ in the blood was followed for 60 min after administration while the biliary and urinary excretion of LTC₄ and its metabolites were determined over a 120 min interval. The total recovery of radioactivity in bile and urine was 45% ± 1 (n = 3) and 18% (n = 2) respectively. Examination of the radioactive metabolites in bile showed LTD₄ (44% of biliary content) and LTE₄ (21% of biliary content) as the major identified lipoxygenase products at t (27 min). The only identified cysteinyl leukotriene observed in the urine was LTE₄ (13% of urinary content). In both bile and urine substantial amount of radioactivity were detected at the solvent front of the reverse phase chromatographic system indicating the presence of additional unidentified metabolites. We suggest that measurement of metabolites using these sampling methods may be useful for the detection and measurement of peptide leukotriene production .     

Profiling circulating and urinary bile acids in patients with biliary obstruction before and after biliary stenting

Bile acids are considered as extremely toxic at the high concentrations reached during bile duct obstruction, but each acid displays variable cytotoxic properties. This study investigates how biliary obstruction and restoration of bile flow interferes with urinary and circulating levels of 17 common bile acids. Bile acids (conjugated and unconjugated) were quantified by liquid chromatography coupled with tandem mass spectrometry in serum and urine samples from 17 patients (8 men and 9 women) with biliary obstruction, before and after biliary stenting. Results were compared with serum concentrations measured in 40 age- and sex-paired control donors (20 men and 20 women). The total circulating bile acid concentration increases from 2.7 μM in control donors to 156.9 μM in untreated patients with biliary stenosis. Serum taurocholic and glycocholic acids exhibit 304- and 241-fold accumulations in patients with biliary obstruction compared to controls. The enrichment in chenodeoxycholic acid species reached a maximum of only 39-fold, while all secondary and 6α-hydroxylated species--except taurolithocholic acids--were either unchanged or significantly reduced. Stenting was efficient in restoring an almost normal circulating profile and in reducing urinary bile acids. Conclusion: These results demonstrate that biliary obstruction affects differentially the circulating and/or urinary levels of the various bile acids. The observation that the most drastically affected acids correspond to the less toxic species supports the activation of self-protecting mechanisms aimed at limiting the inherent toxicity of bile acids in face of biliary obstruction.     

Ellagic acid inhibited 2-aminofluorene and p-aminobenzoic acid acetylation by mononuclear leucocytes from Sprague-Dawley rats

Following exposure of rats to the arylamine carcinogen 2-aminofluorene, DNA-carcinogen adducts were found in the liver and bladder target tissues, and also in circulating leucocytes. This work investigated the effect of ellagic acid on arylamine (2-aminofluorene and p-aminobenzoic acid) acetylations in rat leucocytes. Evidence is presented that rat mononuclear leucocytes are capable of acetylating 2-aminofluorene and p-aminobenzoic acid. Both lymphocytes and monocytes were able to acetylate arylamines during 18 h of culture. Cultured lymphocytes produced about twice as much N-acetyl-2-aminofluorene from 2-aminofluorene and 2.2-fold as much N-acetyl-p-aminobenzoic acid from p-aminobenzoic acid as monocytes. After cotreatment with ellagic acid the lymphocyte and monocyte cultures indicated that ellagic acid reduced 2-aminofluorene acetylation.     

Urinary excretion of free glucocorticosteroids and testosterone in the Mongolian gerbil (Meriones unguiculatus): effects of long-acting corticotrophin and human gonadotrophin

1. Methods for the quantitative collection of 24-hr urines of small laboratory animals and for the measurement of urinary free glucocorticosteroids and testosterone are described. 2. Urinary glucocorticosteroids and testosterone were determined in 0.1-0.5 ml-aliquots of 1/100 diluted urines after kieselgur mini-column extraction. 3. Excretion of glucocorticosteroids and testosterone in undisturbed Mongolian gerbils was 329 and 13 ng/day, respectively. 4. Administration of long-acting (1-24)ACTH (20 IU/animal) increased glucocorticosteroid and testosterone excretion to about 2000 ng/day (glucocorticosteroids) and to about 30 ng/day (testosterone) over 3 days. 5. In animals injected with 100 IU/animal HCG, testosterone excretion was elevated to about 35-50 ng/day over 3 days. 6. As the results show, the measurement of urinary excretion of free glucocorticosteroids and testosterone is a reliable index of adrenal-gonadal function in the Mongolian gerbil. 7. Furthermore, in small laboratory animals, steroid measurements in 24-hr urines may be superior to determinations in plasma, since amounts of urinary steroid are relatively high and 24-hr urines can be collected over longer time periods without stressing the animals.     

Effects of environmental lead levels on the urinary kallikrein excretion of exposed workers

Ten men, working in a factory making car batteries, were hospitalized in order to establish the diagnosis of lead intoxication. The urinary kallikrein activity, determined in their 24-hr urines, was found to be lower than that of a control group. Kallikrein activity was then determined in morning urines of another group of 25 lead exposed men working in the same factory. The urines of this group were collected before and after some environmental improvements which reduced lead concentration in the factory ambient air. The urinary kallikrein excretion of exposed workers was very low before environmental improvements. After the lead reduction in the environmental air, the urinary kallikrein excretion of the same workers was significantly increased; nevertheless, it remained still lower than the control group.     

Biliary, fecal and urinary excretion of [3H]-prostaglandins in the rat

The profiles of biliary, fecal and urinary excretion of tritium labeled prostaglandins (PG's) of differing biological activity were investigated in the rat. The PG's (10 micrograms/kg: 2 to 50 microCi/rat, in 1 ml polyethylene glycol-400) were administered intragastrically. Excretion data were expressed as a percentage of the total administered radioactivity. For the orally administered PG's 11R-methyl-16R-fluoro-15R-hydroxy-9-oxoprosta-ci s-5-trans-13-dienoic acid and its methyl ester, excretion was equally divided between urine and feces. The fecal and urinary profile of excretion of 3H after prostacyclin (PGI2) was similar to that following administration of 11R, 16, 16-trimethyl-15R-hydroxy-9-oxoprosta-cis-5-trans-13-dienoic acid (trimoprostil), a PG with antisecretory-antiulcer potential. However, PGI2 was very poorly absorbed from the intestine, while the absorption of trimoprostil was very efficient. Biliary excretion, with little entero-porto-hepatic biliary circulation, was the main route of elimination of trimoprostil, thereby resulting in rapid elimination of drug-related products and diminishing the potential for systemic liability in the rat.     

Arylamine N-acetyltransferase and arylalkylamine N-acetyltransferase in the mammalian pineal gland

Amine N-acetylation in the pineal gland is of special importance because it is the first step in the synthesis of melatonin from serotonin. In the present study the N-acetylation of arylamines and arylalkylamines by homogenates of rat and sheep pineal glands was investigated. The arylamines studied were p-phenetidine and aniline; the arylalkylamines studied were tryptamine, serotonin, 5-methoxytryptamine, 6-fluorotryptamine, and phenylethylamine. These amines were acetylated by pineal homogenates of both species, although marked interspecies differences in apparent Km and Vmax values were found. A series of observations in both species indicate that aromatic amine N-acetylation is catalyzed by two distinct enzymes; one preferentially acetylates arylamines and the other preferentially acetylates arylalkylamines. First, isoproterenol treatment of the rat increased arylalkylamine N-acetylation 100-fold without increasing arylamine N-acetylation. Second, cycloheximide treatment in sheep reduced arylalkylamine N-acetylation at night to one-tenth control values, without altering arylamine N-acetylation. Third, arylamine N-acetyltransferase and arylalkylamine N-acetyltransferase inactivated at different rates at 4 degrees C. Fourth, the two enzymes were resolved by size exclusion chromatography. These results clearly establish that the pineal gland contains an arylamine N-acetyltransferase and a second, independently regulated arylalkylamine N-acetyltransferase which appears to be primarily responsible for the physiological conversion of serotonin to melatonin via the intermediate N-acetylserotonin.     

Biliary and urinary excretion rates and serum concentration changes of four bilirubin photoproducts in Gunn rats during total darkness and low or high illumination.

On cycled exposure of Gunn rats to total darkness and low and high illumination, biliary excretion rates of (EZ)- and (ZE)-bilirubin and (EZ)-cyclobilirubin increased up to approx. 10-fold from the mean basal values of 1.2 and 0.2 microgram/h to the mean maximum values of 25.2 and 4.2 micrograms/h respectively, and at the same time those of (EE)-bilirubin and (EE)-cyclobilirubin also increased, but at very much lower rates than those of the first-mentioned two. During the low illumination only (EZ)- and (ZE)-bilirubin and (EZ)-cyclobilirubin appeared in the urine; during the high illumination (EE)-bilirubin and (EE)-cyclobilirubin also appeared, showing a similar excretion pattern to that observed in the bile, but the total urinary excretion rates were lower than the total biliary excretion rates. The serum bilirubin concentrations fell gradually to lower values, accompanied by an increment in (EZ)- and (ZE)-bilirubin, but (EZ)-cyclobilirubin was not detected. It is concluded that during phototherapy the predominant pathway for the removal of bilirubin from the body in the Gunn rat is by biliary excretion of the geometric photoisomers (EZ)- and (ZE)-bilirubin, derived from Z----E isomerization, and the structural photoisomer (EZ)-cyclobilirubin, formed from intramolecular endo-vinyl cyclization.     

Studies on flavonoid metabolism. Biliary and urinary excretion of metabolites of (+)-[U-14C]catechin

1. The biliary and urinary excretion of (+)-[U-(14)C]catechin was studied in normal male rats after a single injection of the flavonoid. 2. In rats large amounts of radioactivity (33.6-44.3% of the dose in 24h) were excreted in the bile as two glucuronide conjugates [one of which was a (+)-catechin conjugate] and three other unconjugated metabolites. 3. Excretion of radioactivity in the urine when the bile duct was not cannulated amounted to 44.5% of the dose. 4. In both the urine and bile the new metabolites showed maximum excretion in the (1/2)-1(1/2)h after intravenous injection of [(14)C]catechin. 5. The metabolites m-hydroxyphenylpropionic acid, p-hydroxyphenylpropionic acid, delta-(3-hydroxyphenyl)-gamma-valerolactone and delta-(3,4-dihydroxyphenyl)-gamma-valerolactione originate from the action of the intestinal micro-organisms on the biliary-excreted metabolites of (+)-catechin. These phenolic acid and lactone metabolites are then reabsorped and excreted in the urine. 6. It is proposed that, depending on the route of administration of (+)-catechin, there exists an alternative pathway, involving biliary excretion, for the metabolism of (+)-catechin.     

Effect of ML-236B (compactin) on biliary excretion of bile salts and lipids, and on bile flow, in the rat

To assess the importance of de novo cholesterol synthesis for bile salt formation, the effects of ML-236B (an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase) on biliary excretion of bile salts and lipids were studied in rats with permanent catheters in bile duct, heart and duodenum. In rats having their bile diverted continuously for 8 days, duodenal administration of ML-236B (50 mg/kg) caused an immediate transient choleresis, which subsided after 2 h. Concomitant with the choleresis concentrations of bile salt, phospholipid and cholesterol fell, but this decrease was maintained for 6 h. Consequently, ML-236B inhibited biliary output salts and lipids from the second till the sixth hour after injection. The kinetics of biliary excretion of intravenously injected [14C]taurocholate were not affected by ML-236B administration. In rats having their biliary catheter connected to the duodenal catheter, or in rats with prolonged bile diversion but treated with mevalonolactone, ML-236B again caused a transient choleresis (having subsided after 2 h), but now did not affect biliary excretion of bile salts and lipids. It is concluded that (1) ML-236B causes a transient bile salt-independent choleresis, (2) ML-236B depresses excretion of bile salts and lipids by blocking mevalonate synthesis and not by blocking the bile salt or lipid transport, (3) biliary excretions of phospholipids and cholesterol partly depend on excretion of bile salt, and (4) in rats with a prolonged total bile diversion newly formed mevalonate is a major substrate for bile salt synthesis.     

Mrp2 is involved in benzylpenicillin-induced choleresis

Benzylpenicillin (PCG; 180 micromol/kg), a classic beta-lactam antibiotic, was intravenously given to Sprague-Dawley (SD) rats and multidrug resistance-associated protein 2 (Mrp2)-deficient Eisai hyperbilirubinemic rats (EHBR). A percentage of the [(3)H]PCG was excreted into the bile of the rats within 60 min (SD rats: 31.7% and EHBR: 4.3%). Remarkably, a transient increase in the bile flow ( approximately 2-fold) and a slight increase in the total biliary bilirubin excretion were observed in SD rats but not in the EHBR after PCG administration. This suggests that the biliary excretion of PCG and its choleretic effect are Mrp2-dependent. Positive correlations were observed between the biliary excretion rate of PCG and bile flow (r(2) = 0.768) and more remarkably between the biliary excretion rate of GSH and bile flow (r(2) = 0.968). No ATP-dependent uptake of [(3)H]PCG was observed in Mrp2-expressing Sf9 membrane vesicles, whereas other forms of Mrp2-substrate transport were stimulated in the presence of PCG. GSH efflux mediated by human MRP2 expressed in Madin-Darby canine kidney II cells was enhanced in the presence of PCG in a concentration-dependent manner. In conclusion, the choleretic effect of PCG is caused by the stimulation of biliary GSH efflux as well as the concentrative biliary excretion of PCG itself, both of which were Mrp2 dependent.     

Lack of biliary lipid excretion in the little skate, Raja erinacea, indicates the absence of functional Mdr2, Abcg5, and Abcg8 transporters

The ABC transporters bile salt export pump (BSEP; encoded by the ABCB11 gene), MDR3 P-glycoprotein (ABCB4), and sterolin 1 and 2 (ABCG5 and ABCG8) are crucial for the excretion of bile salt, phospholipid, and cholesterol, respectively, into the bile of mammals. The current paradigm is that phospholipid excretion mainly serves to protect membranes of the biliary tree against bile salt micelles. Bile salt composition and cytotoxicity, however, differ greatly between species. We investigated whether biliary phospholipid and cholesterol excretion occurs in a primitive species, the little skate, which almost exclusively excretes the sulphated bile alcohol scymnolsulphate. We observed no phospholipid and very little cholesterol excretion into bile of these animals. Conversely, when scymnolsulphate was added to the perfusate of isolated mouse liver perfusions, it was very well capable of driving biliary phospholipid and cholesterol excretion. Furthermore, in an erythrocyte cytolysis assay, scymnolsulphate was found to be at least as cytotoxic as taurocholate. These results demonstrate that the little skate does not have a system for the excretion of phospholipid and cholesterol and that both the MDR3 and the two half-transporter genes, ABCG5 and ABCG8, have evolved relatively late in evolution to mediate biliary lipid excretion. Little skate plasma membranes may be protected against bile salt micelles mainly by their high sphingomyelin content.     

Relations between urinary 3-methoxytyramine and the peripheral metabolism of dopamine in human adults and children]

3-Methoxytyramine (3-MT), the direct metabolite of dopamine (DA) is present in human urines at birth. The rate of its urinary excretion (microgram/24 h) increases highly from birth to 12 months of age; in the next period of infancy, the increase is slower and parallel to that of creatininury; after 15 years, the urinary amounts of 3-MT remain nearly constant, with advancing age. The analysis of the possible sources of urinary 3-MT, lead us to suggest that this compound has essentially a peripheral origin. On the other hand the comparison between urinary data of 3-MT and DA in normal infants and adult subjects has shown that 3-MT excretion is less affected by dietary input than DA itself, so that it can be concluded that urinary 3-MT is a better indication of peripheral dopaminergic activity than urinary DA, chiefly in the young child.     

Characterization of serum and urinary bile acids in patients with primary biliary cirrhosis by gas-liquid chromatography-mass spectrometry: effect of ursodeoxycholic acid treatment

We have studied the effect of ursodeoxycholic acid on the serum and urinary bile acids in seven patients with moderate to severe primary biliary cirrhosis. Bile acids were characterized by gas-liquid chromatography-mass spectrometry and quantified by capillary gas-liquid chromatography. Serum bile acids were elevated 26-fold over control values, with 2.2 times more cholic acid than chenodeoxycholic acid. Urinary bile acid output was elevated 22-fold over control values with a cholic acid:chenodeoxycholic acid ratio of 1.6. In addition, lithocholic acid, deoxycholic acid, ursodeoxycholic acid, 1 beta-hydroxycholic acid, 1 beta-hydroxydeoxycholic acid, and hyocholic acid were identified in both serum and urine; the proportions of the 1- and 6-hydroxylated bile acids were much higher in urine than in serum of the patients (32.1% versus 4.2%). Three months of placebo administration did not change the serum and urinary bile acid composition. In contrast, ursodeoxycholic acid feeding (12-15 mg/kg body weight per day) for 6 months resulted in a 25% decline in the total serum bile acid concentration from the pretreatment values. The proportion of ursodeoxycholic acid increased from 2.1 to 41.2% of total bile acids, so that total fasting serum endogenous bile acid levels decreased 62.4%. Ursodeoxycholic acid feeding substantially increased urinary bile acid output, with ursodeoxycholic acid comprising 58.1%. The proportion of 1- and 6- hydroxylated endogenous bile acids was reduced by 45.5% from pretreatment levels and approximately 4.5% of the urinary bile acids were omega-muricholic acid, 1 beta-hydroxyursodeoxycholic acid, and 21-hydroxyursodeoxycholic acid. These results demonstrate significant changes in the serum and urinary bile acid pattern in primary biliary cirrhosis during ursodeoxycholic acid treatment. The beneficial effect of ursodeoxycholic acid may be due to reduction of the hydroxylated derivatives of endogenous bile acids together with the appearance of hydroxylated derivatives of ursodeoxycholic acid or it may be due to displacement of the more hydrophobic endogenous bile acids by the hydrophilic ursodeoxycholic acid.     

Role of the hepatocyte microtubular system in the excretion of bile salts and biliary lipid: implications for intracellular vesicular transport

The role of the hepatocyte microtubular system in the transport and excretion of bile salts and biliary lipid has not been defined. In this study the effects of microtubule inhibition on biliary excretion of micelle- and non-micelle-forming bile salts and associated lipid were examined in rats. Low-dose colchicine pretreatment had no effect on the baseline excretion of biliary bile salts and phospholipid in animals studied 1 hr after surgery (basal animals), but slightly retarded the excretion of tracer [14C]taurocholate relative to that of lumicolchicine-pretreated (control) rats. However, colchicine pretreatment resulted in a marked reduction in the excretion of 2 mumol/100 g doses of a series of four micelle-forming bile salts of differing hydrophilicity, but had no significant effect on the excretion of the non-micelle-forming bile salt, taurodehydrocholate. Continuous infusion of 0.2 mumol of taurocholate/(100 g.min) following 24 hr of biliary drainage (depleted/reinfused animals) resulted in physiologic bile flow with biliary excretion rates of bile salts, phospholipid, and cholesterol that were markedly inhibited (mean 33, 39, and 42%, respectively) by colchicine or vinblastine pretreatment. Excretion of tracer [14C]taurocholate also was markedly delayed by colchicine in these bile salt-depleted/reinfused animals. In contrast, colchicine did not inhibit bile salt excretion in response to reinfusion of taurodehydrocholate. Thus, under basal conditions, the microtubular system appears to play a minor role in hepatic transport and excretion of bile salts and biliary lipid. However, biliary excretion of micelle-forming bile salts and associated phospholipid and cholesterol becomes increasingly dependent on microtubular integrity as the transcellular flux and biliary excretion of bile salts increases, in both bile salt-depleted and basal animals. We postulate that cotransport of micelle-forming bile salts and lipids destined for biliary excretion, via an intracellular vesicular pathway, forms the basis for this microtubule dependence.     

Biliary excretion of [C]succinylsulphathiazole in the rat and rabbit

1. After intravenous injection about 30% of the dose (20mg./kg.) of succinylsulphathiazole is excreted unchanged in the bile in 3hr. by the rat, whereas only about 1% is excreted by the rabbit. When the renal pedicles are ligated the biliary excretion of succinylsulphathiazole in the rat increases to about 80% of the dose, but in the rabbit under these conditions the biliary excretion is only 2% of the dose. 2. In the rat, the sulphonamide readily enters the liver and biliary excretion occurs against a concentration gradient from liver to bile; further, the excretory process can be saturated, and can be depressed by the simultaneous administration of phenolphthalein glucuronide or bile salts. 3. In the rabbit, these conditions have not been found; succinylsulphathiazole does not readily enter the liver from the plasma, there is no transfer of the drug from the liver cells to the bile against a concentration gradient, and no saturation or depression of the biliary excretion of succinylsulphathiazole is found. 4. It is suggested that two factors responsible, at least partly, for the low biliary excretion of succinylsulphathiazole in the rabbit are the poor entry of the sulphonamide into the liver in this species and a deficiency of the concentrative mechanism for its excretion in the bile.     

Quantitative evaluation of the effects of human carcinogens and related chemicals on human foreskin fibroblasts

Ten compounds representative of diverse classes of chemicals were evaluated for their cytotoxicity and transforming ability to human skin fibroblasts in vitro. Only five of the ten compounds were highly cytotoxic in the 0-100 µg/ml range and their order of cytotoxicity was: 2,5-bis(1-aziridinyl)-3,6-bis(carboethoxyamino)-1,4-benzoquinone (AZQ) > cis platin > bis(chloromethyl)ether (BCME) > acrylonitrile > afatoxin BI (AFBI). The other five compounds, afatoxin B2 (AFB2), methylmethacrylate, 1-naphthylamine (1-NA), 2-naphthylamine (2-NA), and cyclophosphamide, exhibited less than 40% inhibition of colony formation even at 100 µg/ml of the compound (the maximum concentration of AFB2 used was 50 µg/ml due to its low solubility). Anchorage-independent growth of exposed cells in soft agar was used as a biological endpoint for the expression of chemical transformation. AFB₁ had strong transforming ability, whereas AFB₂ was a weak transforming agent. The transforming abilities of acrylonitrile, AZQ, BCME, cis-platin, methylmethacrylate and 2-NA ranged between those of AFBI and AFB2. 1-NA also induced the soft agar growth property in the treated cells even though this compound has not been shown to be carcinogenic. AFB₁, AZQ, cisplatin, cyclophosphamide and 1-NA exhibited a dose dependent increase in soft agar growth frequency for at least three consecutive concentrations. The data suggest that anchorage-independent colony forming ability of exposed cells is a reliable marker to measure the carcinogenic potential of various hazardous chemicals.Abbreviations AZQ 2,5-bis(1-aziridinyl)-3,6-bis(carboethoxyamino)-1,4-benzoquinone - AFB aflatoxin B₁ - AFB2 aflatoxin 132 - AI anchorage independent - B[a]P benzo[a]pyrene - BCME bis(chloromethyl)ether; cis-platin, cis-diammine-dichloroplatinum - CM complete medium - E.D.50 effective dose which produced 50% cytotoxicity - CP cyclophosphamide - HNF human neonatal foreskin - HPLC high pressure liquid chromatography - 1-NA 1-naphthylamine - 2-NA 2-naphthylamine - PDL population doubling     

Spectroscopic investigation of the interaction of the toxicant, 2-naphthylamine, with bovine serum albumin

The mechanism of interaction between bovine serum albumin (BSA) and 2-naphthylamine (2-NA) in aqueous solution was investigated by fluorescence spectroscopy, circular dichroism (CD) spectra, and UV-vis spectroscopy. It was proved from fluorescence spectra that the fluorescence quenching of BSA by 2-NA was a result of the formation of complex between 2-NA and BSA, and the binding constants (K(a) ) as well as the numbers of binding sites for 2-NA in BSA were determined according to the modified Stern-Volmer equation. The results of synchronous fluorescence and CD spectra demonstrated 2-NA could decrease the amount of α-helix of BSA, leading to the loosening of protein skeleton. UV-vis spectroscopy and resonance light scattering spectra (RLS) results also suggested the conformation of BSA were changed and the BSA aggregation occured, which could induce toxic effects on the organism.