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Organophosphorus pesticides (OPs) are a public health concern due to their worldwide use and documented human exposures. Phosphorothioate OPs are metabolized by cytochrome P450s (P450s) through either a dearylation reaction to form an inactive metabolite, or through a desulfuration reaction to form an active oxon metabolite, which is a potent cholinesterase inhibitor. This study investigated the rate of desulfuration (activation) and dearylation (detoxification) of methyl parathion and diazinon in human liver microsomes. In addition, recombinant human P450s were used to determine the P450-specific kinetic parameters (Kmand Vmax) for each compound for future use in refining human physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) models of OP exposure. The primary enzymes involved in bioactivation of methyl parathion were CYP2B6 (Km= 1.25 μM; Vmax= 9.78 nmol · min–1· nmol P450–1), CYP2C19 (Km= 1.03 μM; Vmax= 4.67 nmol · min–1· nmol P450–1), and CYP1A2 (Km= 1.96 μM; Vmax= 5.14 nmol · min–1· nmol P450–1), and the bioactivation of diazinon was mediated primarily by CYP1A1 (Km= 3.05 μM; Vmax= 2.35 nmol · min–1· nmol P450–1), CYP2C19 (Km= 7.74 μM; Vmax= 4.14 nmol · min–1· nmol P450–1), and CYP2B6 (Km= 14.83 μM; Vmax= 5.44 nmol · min–1· nmol P450–1). P450-mediated detoxification of methyl parathion only occurred to a limited extent with CYP1A2 (Km= 16.8 μM; Vmax= 1.38 nmol · min–1· nmol P450–1) and 3A4 (Km= 104 μM; Vmax= 5.15 nmol · min–1· nmol P450–1), whereas the major enzyme involved in diazinon detoxification was CYP2C19 (Km= 5.04 μM; Vmax= 5.58 nmol · min–1· nmol P450–1). The OP- and P450-specific kinetic values will be helpful for future use in refining human PBPK/PD models of OP exposure.

Organophosphorus pesticides (OPs) remain a potential concern to human health because of their continuing worldwide use. Thiophosphorus OPs, once bioactivated by cytochromes P450 (P450s), form oxon metabolites, which are potent acetylcholinesterase inhibitors. This study investigated the rate of desulfation (activation) and dearylation (detoxification) of parathion and chlorpyrifos in human liver microsomes. In addition, recombinant human P450s were used to quantify, for the first time, the P450-specific kinetic variables (Kmand Vmax) for each compound for future use in refining human physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) models of OP exposure. CYP1A2, 2B6, 2C9, 2C19, 3A4, 3A5, and 3A7 were found to be active to a widely varying degree in parathion metabolism, whereas all, with the exception of CYP2C9, were also found to be active in chlorpyrifos metabolism. CYP2B6 and CYP2C19 demonstrated low Kmand high Vmaxvalues for the metabolism of both model compounds, which supports their role as the primary enzymes that regulate metabolism at low-level human exposures to OPs. With Kmand Vmaxvalues of 0.61 µM, 4827 pmol/min/nmol P450 and 0.81 µM, 12,544 pmol/min/nmol for formation of paraoxon and chlorpyrifos-oxon, respectively, CYP2B6 favored the desulfation reaction. CYP2C19 activity favored dearylation with Kmand Vmaxvalues of 0.60 µM, 2338 pmol/min/nmol P450 and 1.63 µM, 13,128 pmol/min/nmol for formation of p-nitrophenol and 3,4,5-tricholorpyrindinol, respectively. P450-specific kinetic parameters for OP metabolism will be used with age-dependent hepatic P450 content to enhance PBPK/PD models so that OP exposures can be modeled to protect human health in different age groups.

Organochlorines, such as 2,2-bis (4-chlorophenyl)-1,1-dichloroethylene (DDE), polychlorinated biphenyls (PCBs), and hexachlorobenzene (HCB) are lipophilic compounds that are ubiquitous in the environment and may cause adverse health effects in humans. We examined the correlation between epidemiological exposure variables and serum DDE, PCB, and HCB levels in a sample of 192 healthy, female postmenopausal western New York residents; a subset of the control group from a case–control study on breast cancer risk. Usual diet, reproductive and medical histories, and other lifestyle information were obtained by an extensive in person interview. Serum levels (ng/g) of DDE, HCB, and 69 PCB congeners were determined by gas chromatography with electron capture detection. Statistical analyses included computations of crude and age and lipid adjusted correlation coefficients, as well as multiple linear regression analysis. Results indicated that the strongest predictors for serum DDE levels were age, serum lipids, parity, and fruit and dairy consumption. Statistically significant predictors of PCB levels included age, serum lipids, parity, and fish consumption. Serum HCB levels were related to age, serum lipids, and fruit and red meat consumption. Our findings are consistent with previous investigations that reported strong associations between organochlorine levels and age and serum lipids. The absence of other data showing an association between fruit intake and organochlorine levels make the importance of this finding unclear. Am. J. Ind. Med. 41:102–110, 2002. © 2002 Wiley-Liss, Inc.

Lactating female members and spouses of male members of the New York State Angler Cohort who agreed to provide breast milk samples were the subjects of this study. Questionnaires were provided to participants focusing on Lake Ontario fish consumption, reproductive history, and lactation history. Milk samples were analyzed for 77 polychlorinated biphenyls (PCB) congeners, 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (DDE), a metabolite of dichlorodiphenyltrichloroethane (DDT), hexachlorobenzene (HCB), and 1,1a,2,2,3,3a, 4,5,5,5a,5b,6-dodecachlorooctahydro-1,3,4-methano-1H-cyclobuta[cd]pentalene (Mirex). The percentage of samples with quantifiable levels, above the limit of detection (LOD), varied among the individual congeners from 10 to 100%. Nine PCB congeners (designated by their IUPAC No.) and DDE were found in all of the 100 samples analyzed. These include the following, in decreasing order of concentration: DDE>153>138>180>118>187>188>177>200. Total PCB concentrations were estimated by taking the sum of the concentrations of all PCB congeners (up to 77 congeners) above their respective LOD in a given sample. PCB concentrations increased with increasing concentration of milk lipid. Lipid adjusted PCB concentrations increased as a function of maternal age. PCB congener profiles in milk favored the higher chlorinated congeners, with the four highest congeners having 5 to 7 chlorine atoms. Fish eaters had a significantly higher level of several major PCB congeners with congeners 153 and 138 being 1.36 and 1.34 times higher, respectively. PCB and DDE concentrations, expressed on a lipid basis, varied inversely with parity. The total number of months of lifetime lactation varied inversely with the total PCB concentration in breast milk. A similar relationship was evident for DDE. These data are of use for risk assessment in estimating the relative exposure to these environmental contaminants in breast fed infants whose mothers consumed contaminated Lake Ontario fish.

The aquatic ecosystems of the Great Lakes are contaminated with a variety of compounds, some of which are considered reproductive toxicants. Few studies of paternal fish consumption and reproductive endpoints have been undertaken and serve as the impetus for study. Standardized telephone interviews were conducted with 2445 female members of the New York State Angler Cohort (82% response) to update reproductive profiles and to ascertain specific information on time-to-pregnancy (TTP). The study sample includes women with a known TTP and paternal fish consumption data (n=785). Conception delay was defined as more than 12 cycles of unprotected intercourse to achieve pregnancy. Paternal fish consumption was assessed by three measures: frequency of Lake Ontario sport fish meals in 1991, numbers of years eating fish, and estimated PCB exposure from fish consumption. Adjusted ORs for number of fish meals, based on logistic regression, ranged from 0.69 to 0.80; from 0.61 to 0.82 for number of years eating fish; and from 0.44 to 1.14 for quartiles of estimated PCB exposure from fish consumption. All confidence intervals included one. These findings suggest that, based on paternal self-reports, Lake Ontario fish consumption does not increase the risk of conception delay.

Samples of blood and milk were obtained from lactating women participating in the New York State Angler study. A total of seven women gave one blood and one milk sample at time intervals between blood and milk collection different for each woman. The time between samples varied from 3 to 318 days. One subject provided a second milk sample 219 days after the first milk sample. The samples were analyzed for 69 PCB congeners, DDE (a metabolite of DDT), Mirex, and hexachlorobenzene (HCB). Lipid content was determined by gravimetric analysis. The congener profiles in serum and milk were similar for each individual but different among all subjects. The sum of the concentrations of the congeners present above the limit of detection was used to estimate the total PCB concentration that was in the range of 2.6 to 5.8 ng/g of serum and 3.5 to 14.1 ng/g of milk. The ratio of serum to milk concentrations varied from 0.18 to 1.66 with a mean of 0.65±0.49 showing no consistency among individuals prior to adjusting the data for lipid content. The total PCB levels normalized for lipid content were 320–728 ng/g of serum lipid and 239–428 ng/g of milk lipid. The range of the lipid adjusted serum/milk ratio was 1.1 to 2.8 and the mean±SD serum/milk ratio was 1.9±0.5. The ranges of lipid adjusted serum concentration of DDE, HCB, and Mirex were 95 to 591, 8 to 48, and 3 to 29 ng/g lipid, respectively. The ranges of lipid adjusted milk concentration of DDE, HCB, and Mirex were 90 to 577, 11 to 22, and 1 to 10 ng/g lipid, respectively. For DDE, HCB, and Mirex, the means of the individual lipid adjusted serum to milk ratios were 1.5±0.7, 2.5±1.5, and 5.3±4.6, respectively. Considerable differences were found among lipid adjusted concentrations of these environmental pollutants in serum and milk samples from the same individual. This suggests that body burden estimates in lactating women using different matrices may not be equivalent even when lipid adjusted values are used.

Administration to rats of 1,3-difluoro-2-propanol (100 mg kg⁻¹ body weight), the major ingredient of the pesticide gliftor, resulted in accumulation of citrate in the kidney after a 3 hour lag phase. 1,3-Difluro-2-propanol was found to be metabolized to 1,3-difluoroacetone and ultimately to the aconitate hydratase inhibitor (-) erythrofluorocitrate and free fluoride. The conversion of 1,3-difluoro-2-propanol to 1,3-difluoroacetone was found to be catalyzed by an NAD⁺-dependent alcohol dehydrogenase, while the defluorination was attributed to microsomal monooxygenase activity induced by phenobarbitone and inhibited by piperonyl butoxide. 4-Methylpyrazole was found to inhibit both of these processes in vitro and when administered (90 mg kg⁻¹ body weight) to rats, 2 hours prior to 1,3-difluoro-2-propanol, eliminated signs of poisoning, prevented (-) erythrofluorocitrate synthesis, and markedly decreased citrate and fluoride accumulation in vivo. 4-Methylpyrazole also appeared to diminish (-) erythrofluorocitrate synthesis from fluoroacetate in vivo, and this was attributed to its capacity to inhibit malate dehydrogenase activity. The antidotal potential of 4-methylpyrazole and the potential for 1,3-difluoro-2-propanol to replace fluoroacetate (compound 1080) as a vertebrate pesticide is discussed. © 1997 John Wiley & Sons, Inc. J Biochem Toxicol 12: 41–52, 1998

A 70-year-old white female presented approximately 24 h after ingesting three 475 mg tablets (1.425 g) of mercuric chloride in a suicide attempt. Acute renal failure necessitated the initiation of haemodialysis approximately 4 d after the ingestion. Treatment with BAL (2,3-dimercaptopropanol) resulted in only small increases in mercury output into dialysate. A new procedure involving the extracorporeal infusion of the chelating agent dimercaptosuccinic acid (DMSA) into the arterial blood line during haemodialysis was initiated. This procedure of Extracorporeal Regional Complexing Haemodialysis (ERCH) had been effective in increasing methylmercury removal in patients poisoned by contaminated grain. The first DMSA-ERCH procedure was performed 6 d after poisoning. There was a dramatic increase in mercury output into the dialysate. During three treatment sessions of 80 min each, 1189 μg of mercury were removed from the patient. The dialysed mercury represented the only mercury output since the patient was anuric and not producing faeces. DMSA-ERCH appears to be much more effective than BAL and haemodialysis in the treatment of acute inorganic mercury poisoning. The long interval between poisoning and initiation of treatment probably contributed to the patients ultimate demise, 28 d after poisoning. Efficacy of the DMSA-ERCH procedure for inorganic mercury poisoning is likely to be improved as the interval between exposure and treatment is reduced.

Fluoraocetate-specific defluorinase, an enzyme which catalyzes the release of fluoride ion from the rodenticide fluoroacetate, has been purified 347-fold from mouse liver cytosol and shown to be distinct from multiple cationic and anionic glutathione S-transferase isozymes. Fluoroacetate-specific defluorinase was obtained at a final specific activity of 659 nmol of F-/min/mg of protein and was prepared in an overall yield of 12%. The isoelectric point of this hepatic enzyme was acidic, at pH 6.4, as determined by column chromatofocusing. The molecular weight of the active species was estimated at 41,000, and sodium dodecyl sulfate-polyacrylamide gels of the purified defluorinase demonstrated a predominant subunit, Mr = 27,000. Chromatofocusing completely partitioned the fluoroacetate-specific defluorinase from two separate peaks of murine anionic glutathione S-transferase activity. Rabbit antibodies prepared against the purified hepatic defluorinase quantitatively precipitated native defluorinase from mouse and rat liver, but were unable to immunoprecipitate cationic or anionic glutathione S-transferase enzymes from the same preparation. The evidence presented suggests that fluoroacetate-specific defluorinase and glutathione S-transferase activities are catalyzed by separate proteins present in the cytosol of mouse liver.

The New York State Angler Study will evaluate the association between past and current consumption of contaminated fish from Lake Ontario and both short- and long-term health effects in a population-based cohort. It will measure fish consumption and reproductive and developmental health among 10,518 male anglers and 6,651 of their wives or partners, as well as among 913 female anglers. To characterize exposure among subgroups of the cohort, further analytical methods were developed and implemented to measure specific polychlorinated biphenyls (PCB) congeners, methylmercury, and other substances in biological samples. Exposure assessment has been completed for a stratified random sample of 321 anglers. In addition, analyses for 79 congeners of PCBs are complete for 177 anglers. A special study of duck andturtle consumers currently is underway. Telephone interviews have been completed with 2,454 of the 2,999 women who planned a pregnancy between 1991 and 1994. The entire cohort of male anglers, partners of male anglers, and female anglers has been submitted for matching with the New York State live birth and fetal death registries to obtain lifetime reproductive histories. A medical record abstraction study will assess perinatal and developmental outcomes among the 3,442 births that occurred between 1986 and 1991. Finally, a study of breast milk from currently lactating women is underway, and 215 breast milk samples have been collected from the planned pregnancy subcohort. Progress on each of the study components is discussed herein.

2,3-Dimercaptosuccinic acid (DMSA) has been utilized in chelation therapy and in extracorporal complexing hemodialysis therapy for experimental methylmercury intoxication. In the latter application, substantial excretion of methylmercury occurred by the urinary route. This prompted the current study of the effects of continuous intravenous DMSA infusion therapy on methylmercury kinetics in the dog. A nimals previously dosed with 203Hg-labeled methylmercury at 2.5 mg Hg/kg received a priming dose of DMSA, followed by a continuous iv infusion at dose rates that resulted in DMSA concentrations in plasma similar to those observed during DMSA complexing hemodialysis therapy. The kinetics of 203Hg removal in DMSA-infused dogs was compared with both saline-infused controls and DMSA complexing hemodialysis treated dogs.DMSA infusion therapy resulted in a shift in 203Hg binding within systemic blood from the red-cell fraction into plasma. This was consistent with an observed association of DMSA with the plasma fraction. The shift in 203Hg from red cells into plasma was paralleled by an increase in urinary clearance of 203Hg during the DMSA infusion period. In four dogs treated in this fashion, an average of 6.5 μg of mercury was removed by the urinary route over the 5-h treatment period, compared to 0.007 μg in the saline-infused dogs. Although a similar magnitude of mercury output into urine was observed during DMSA complexing hemodialysis, an additional 5 μg was removed by the dialyzer, making that technique 1.5 times as effective as infusion therapy.Comparing 203Hg tissue concentration after DMSA infusion therapy with the saline-treated controls revealed a 6.5-fold decrease in liver, a 3-fold reduction in kidney, and a 27% reduction in cerebrum. No significant differences were observed in medulla or cerebellum. Histopathology revealed no consistent differences between DMSA-treated and saline-treated animals.The DMSA infusion therapy was effective in causing a rapid removal of 203Hg from animals previously dosed with 203Hg-labeled methylmercury. DMSA infusion therapy may provide a useful therapeutic alternative for methylmercury poisoning when rapid removal of the intoxicant is desired and hemodialysis equipment and expertise are not readily available.

Almost all of the methylmercury (MM) in human blood is protein bound, primarily to sulfhydryl ligands. Sulfhydryl agents such as penicillamine, N-acetylpenicillamine, cysteine and N-acetyleysteine are capable of reversing the protein binding of MM when they are added to whole human blood. The magnitude of the protein binding reversal was similar for each compound as predicted by the determination of their relative affinities for MM in vitro. Concentration-dependent reversals of protein binding of MM in blood was observed at increasing sulfhydryl concentrations from 10-4 to 10-2 M. At 10-2 M, a 55- to 60-fold increase in non-protein-bound plasma MM was observed, when compared to blood with no added sulfhydryl agent. Both the complexing agent and the MM complex formed in blood were readily dialyzable using a Travenol 145 twin coil hemodialyzer. At cysteine concentrations of 10-2 M in whole blood, up to 44 percent of whole blood MM was dialyzed on a single pass at a dialyzer blood flow rate of 55 ml/min. Under the same conditions, up 50 94 percent of plasma cysteine was dialyzed. A system is presented for use in vivo on experimental animals. The potential advantages of this method over existing therapeutic regimens for MM poisoning are discussed.

An extracorporeal regional complexing hemodialysis procedure is described which has been successfully applied for the enhancement of removal of methylmercury in the dog. The procedure utilizes the extracorporeal addition of cysteine to arterial blood entering a hemodialyzer, forming a large pool of complexed dialyzable methylmercury in plasma. Diffusion of this methylmercury complex across the dialyzer membrane into dialysate accounts for large amounts of methylmercury being removed from the animal. In conjunction with methylmercury removal, the majority of the infused cysteine is also removed resulting in comparatively low systemic doses of cysteine to the animal. At blood flow rates of 45 ml/min, and dialysate flow rates of approximately 550 ml/min, the mean percentage of methylmercury cleared from blood passing through the dialyzer was 39%. Rates of elimination of methylmercury from the dog could be increased by a factor of 100 during the extracorporeal regional complexing hemodialysis procedure. Regional collimated counting of radioactivity along the length of the dog revealed a decline in all areas including the head region. The procedure was void of any noticeable side effects during treatment or as evidence by histological evaluation of liver and kidney after treatment.

The gamma-GTP inhibitor L-(alpha S,5S)-alpha-amino-3-chloror-4,5-dihydro-5-isoxazoleacetic acid (AT-125) was administered to CBA/J mice pretreated with 203Hg-methylmercury (MM) (0.5 mg/kg) to determine whether increasing urinary GS in this strain would result in a simultaneously increased urinary elimination of MM. Doses at AT-125 ranging from 3.0 to 30 mg/kg increased urinary GS in a dose-related fashion. The peak effect was attained at 2 hr after injection. AT-125 (7.5 mg/kg) increased urinary GS to peak value of 450 microM. When this dose was administered to mice 24 hr after MM, neither the rate of decline in body burden of 203Hg nor the rate of 203Hg output into urine or feces varied significantly from control values. A dose of 15 mg of AT-125 per kg increased urinary GS to 1.0 mM and caused a significant increase in urinary excretion of 203Hg when compared to the 7.5-mg dose group. The greatest effect was seen at the 30-mg AT-125/kg dose which produced a 1.9 mM concentration of total GS in urine and a 2-fold increase in the urinary 203Hg excretion rate. The dose-dependent changes in urinary excretion elicited by AT-125 were paralleled by increased rates of decline of 203Hg body burden and decreased rates of excretion in the feces. The results suggest that urinary GS must approach the millimolar range before affecting a redistribution of MM across the luminal membrane.

The article presents the author's comments regarding the 'Faith in Tomorrow' plan to redefine Catholic education in the Diocese of Buffalo, New York.