CIIT Centers for Health Research, 6 Davis Drive, PO Box 12137, Research Triangle Park, North Carolina 27709-2137
Received June 28, 2001; accepted October 4, 2001
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ABSTRACT |
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Key Words: hydrogen sulfide; pharmacokinetics; cytochrome oxidase; nasal toxicity; rat; inhalation.
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INTRODUCTION |
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The primary mechanism for the toxic action of H2S is direct inhibition of cytochrome oxidase, an enzyme critical for mitochondrial respiration (Khan et al., 1990; Nicholls and Kim, 1982
). Tissues with high oxygen demand (e.g., brain and heart) are especially sensitive to disruption of oxidative metabolism by H2S (Ammann, 1986
). Human exposure to H2S results in concentration-dependent toxicity in the respiratory, cardiovascular, and nervous systems. Acute human exposure to relatively low concentrations (
50 ppm) of H2S results in ocular and respiratory mucous membrane irritation leading to nasal congestion, pulmonary edema, and a syndrome known as gas eye, which is characterized by corneal inflammation (ATSDR, 1999
; Reiffenstein et al., 1992
). Despite the strong characteristic odor associated with H2S, many exposed individuals are unaware of its presence because their sense of smell is severely impaired following exposure to
150 ppm H2S. Acute human exposure to high concentrations of H2S (e.g.,
500 ppm) results in a rapid onset of respiratory paralysis and unconsciousness that can result in death within minutes (Beauchamp et al., 1984
). Persistent sequelae of H2S poisoning are often related to the olfactory system and may include hyposmia, dysosmia, and phantosmia (Hirsch and Zavala, 1999
; Kilburn, 1997
).
Animal studies confirm that the olfactory system is especially sensitive to H2S inhalation. Acute exposure of rats to moderately high concentrations of H2S ( 80 ppm) resulted in regeneration of the nasal respiratory mucosa and full thickness necrosis of the olfactory mucosa (Brenneman et al., 2001; Lopez et al., 1988b
). Subchronic exposure of rats to 30 or 80 ppm H2S resulted in nasal pathology that was limited to the olfactory epithelium (Brenneman et al., 2000a
). The olfactory mucosal lesions observed in rats following H2S inhalation are not unique. For example, similar patterns of nasal injury were observed following exposure to chlorine, dimethylamine, and other irritant gases (Buckley et al., 1985
; Jiang et al., 1983
; Morgan, 1991
). Comparable olfactory lesions were also observed following parenteral administration of iminodipropionitrile, thus suggesting that systemic delivery may play a role in the nasal toxicity induced by certain chemicals (Genter et al., 1995
). Our laboratory recently demonstrated that systemic delivery of H2S was not an important consideration for this nasal toxicant (Brenneman et al., 2000b
). Regional differences in H2S delivery or uptake, local clearance processes, or differences in cellular sensitivity to the gas more likely contribute to the site-specific distribution of H2S-induced lesions within the rat nose (Morgan and Monticello, 1990
).
Hydrogen sulfide metabolism occurs through three pathways: oxidation, methylation, and reaction with cytochrome c and other metallo- or disulfide-containing proteins (Beauchamp et al., 1984). The major metabolic pathway for H2S is the rapid multistep hepatic oxidation of sulfide to sulfate (Fig. 1
) and subsequent elimination of sulfate in the urine (Bartholomew et al., 1980
; Beauchamp et al., 1984
). Several investigators have examined the toxicokinetics of H2S following inhalation. Kage et al. (1992) reported elevated blood and urinary thiosulfate concentrations in rabbits exposed to 100200 ppm H2S for 60 min. Kangas and Savolainen (1987) likewise reported elevated urinary thiosulfate levels in human volunteers exposed to 8, 18, or 30 ppm H2S for 3045 min. Few studies have examined sulfide concentrations in lung, brain, or other target tissues following H2S inhalation.
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MATERIALS AND METHODS |
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Animals.
A total of 266 9- to 10-week old male CD rats were obtained from Charles River Laboratories, Inc. (Raleigh, NC) and maintained in the CIIT animal facility, which is accredited by the Association for Assessment and Accreditation of Laboratory Animal Care. Animals were individually housed in polycarbonate cages with cellulose fiber chip bedding (ALPHA-driTM, Shepherd Specialty Papers, Kalamazoo, MI) and provided NIH-07 pelleted rodent chow (Zeigler Brothers, Gardners, PA) and deionized filtered tap water ad libitum except during inhalation exposures. Animal rooms were ventilated with HEPA-filtered air and maintained at 18.521.5°C and 4070% humidity on a 12-h lightdark cycle. The study was conducted according to federal guidelines for the care and use of laboratory animals (NRC, 1996) and under the supervision of the CIIT Institutional Animal Care and Use Committee.
Experimental design.
Our first objective was to evaluate the relationship between the concentration of sulfide and cytochrome oxidase activity in known target tissues (i.e., lung and hindbrain) following acute exposure to inhaled H2S. In this experiment, animals (n = 6 rats/exposure concentration) were exposed to 0, 10, 30, 80, 200, or 400 ppm H2S for 3 h. End-of-exposure sulfide concentrations and cytochrome oxidase activity were determined in hindbrain, lung, and liver samples from rats exposed to 200 or 400 ppm H2S. Tissue samples from animals in other H2S exposure groups were evaluated for sulfide concentration or cytochrome oxidase activity if the end-of-exposure value for the end point in the 200-ppm H2S exposure group was significantly different from that observed in an unexposed (control) group. We were also interested in evaluating the time course of the sulfide concentration in a target tissue. This evaluation was performed on lung tissues, as it was the only target organ that demonstrated a clear dose-response relationship between tissue sulfide concentration and cytochrome oxidase inhibition. Lung sulfide concentration was determined at 0, 1.5, 3, 3.25, 3.5, 4, 5, and 7 h after the start of a 3-h exposure (n = 6 rats/exposure concentration/time point) to 400 ppm H2S. Rats from this first experiment were killed by CO2 asphyxiation followed by abdominal exsanguination.
Our second objective was to evaluate whether increased sulfide deposition or enhanced sensitivity to cytochrome oxidase inhibition could account for the increased sensitivity of the rodent olfactory epithelium to H2S inhalation. In this experiment, rats (n = 6 rats/exposure concentration/time point) were exposed to 0, 30, 80, 200, or 400 ppm for 3 h/day for either 1 day or 5 consecutive days. Immediately following the end of the H2S exposure, rats were killed by decapitation, and the head was sectioned sagitally on the bridge of the nose. The nasal respiratory and olfactory mucosa were removed with the supporting ethmoturbinates and flash-frozen in liquid nitrogen. These samples were used for tissue sulfide evaluations (single exposure only) or cytochrome oxidase activity (1- and 5-day exposures).
We were also interested in determining whether subchronic H2S exposure could result in altered lung or hindbrain sulfide concentrations or cytochrome oxidase activity. In order to assess this possibility, we evaluated lung and hindbrain samples for sulfide concentration and cytochrome oxidase activity from male rats exposed for 6 h/day for 70 consecutive days to 0, 10, 30, or 80 ppm H2S. These animals had been used in a reproductive and developmental toxicity study (Dorman et al., 2000) and were subsequently evaluated for H2S-induced nasal pathology (Brenneman et al., 2000a
). Samples were collected immediately after the end of the last H2S exposure and flash-frozen in liquid nitrogen within several minutes after euthanasia.
H2S exposure.
Methods used to generate and characterize the H2S exposure atmospheres have been previously described (Struve et al., 2001). Briefly, gas cylinders containing 5% (50,000 ppm) H2S in nitrogen were purchased from Holox Gases (Cary, NC). Nose-only exposures were conducted using rat nose-only tubes and a nose-only system with 52 exposure ports (Cannon et al., 1983
). Total air flow in the nose-only units was adjusted to provide approximately 0.5 l/min per animal port. Hydrogen sulfide was metered through mass flow controllers (MKS Instruments, Andover, MA) and mixed with the nose-only unit air supply to provide the desired target H2S concentration. Exposure H2S concentrations were determined by gas chromatography-FPD (Hewlett-Packard model 6890 with a GS-Q 30 meter x 0.53 µm Alltech column) at least six times during each 3-h exposure. The generation system was operated by the Andover Infinity control system (Andover Controls Corporation, Andover, MA). Animals were exposed to 0, 10, 30, 80, 200, or 400 ppm H2S for 3 h.
Cytochrome oxidase activity.
Cytochrome oxidase activity was evaluated by determining the rate of oxidation of reduced ferricytochrome c using methods described by Weyant et al. (1988). Bovine-derived ferricytochrome c was initially dissolved (10 mg/ml) in a 0.01 M sodium phosphate buffer (pH = 7.0) and then reduced by the addition of ascorbic acid (2.4 mg/ml) for 24 h. Excess ascorbate was removed by equilibrium dialysis in a 0.01 M sodium phosphate buffer (pH = 7.0) using 3,500 molecular weight cutoff tubing (Spectrum Medical Industries, Los Angeles, CA). Three changes of buffer were performed over a 24-h period. The assay reagent contained 0.7 ml (7 mg) reduced cytochrome c, 1 ml sodium phosphate buffer (pH = 7.0), and 8.3 ml distilled water. The degree of reduction of the final assay mix was measured using a Beckman DV 650 UV/VIS spectrophotometer (Fullerton, CA), and the assay reagent was considered fully reduced if the A550/A565 ratio was greater than 6.5, as specified by the product insert from Worthington Biochemical Corporation (Lakewood, NJ).
The following modifications were made to the methods described by Weyant et al. (1988) to accommodate the use of a COBAS FARA II analyzer (Roche Diagnostic System, Somerville, NJ). Representative 50- to 200-mg tissue samples were diluted 10-fold with a 0.25 M sucrose buffer and homogenized using an ultrasonic sonifier. Tissue homogenates were centrifuged (3000 x g for 10 min at 4°C). The supernatant was removed and added to an equivalent amount of 0.25 M sucrose buffer. The sample was then recentrifuged (3000 x g for 10 min) and the resulting supernatant used for the cytochrome oxidase assay. Enzyme activity was measured by monitoring the oxidation of reduced cytochrome c at 550 nm. Absorbance readings were taken following a 10-s incubation time and at 5-s intervals for 90 s. Total protein concentration within each sample was analyzed with the COBAS FARA II spectrophotometer using commercially available reagents (Roche Diagnostic System, Somerville, NJ).
Determination of tissue sulfide concentrations.
Hindbrain, liver, lung, and nasal epithelium samples from control rats and animals exposed to H2S were evaluated for sulfide content. Tissue samples (50150 mg) were sectioned directly from frozen tissues, weighed, and placed into a clear glass crimp-top vial with molded conical bottom (Sun International, Wilmington, NC). The vials were sealed using a teflon septum, and 1 µl tetraethylammonium hydroxide (TEAH, 35% aqueous solution, SACHEM, Austin, TX) per milligram of sample was added to the vial to digest the sample. The TEAH was added to the vial with a gastight syringe (Hamilton, Reno, NV) in order to minimize loss of H2S due to volatilization. Samples were centrifuged for 5 min at 3000 x g (4°C) and were then kept at room temperature for 24 h to complete the sample digestion. After 24 h, 8 µl of 28 mM NaOH per milligram sample were injected into the vial, and the samples were centrifuged again at 3000 x g for 5 min. A 100-µl sample of the supernatant was then added to 400 µl of 28 mM NaOH in a polypropylene ConSert vial (Sun International, Wilmington, NC) to complete a 50-fold dilution of the tissue sample. The diluted supernatant sample was then injected into the liquid chromatography system.
Sulfide and its metabolites were separated by high-performance liquid chromatography (HPLC) using methods adapted from Mitchell et al. (1993) and Rocklin and Johnson (1983). The liquid chromatogram consisted of a Model 580 dual-piston solvent delivery module (ESA Inc., Chelmsford, MA), a pulse-dampener, a Waters 717 plus refrigerated autosampler (Millipore Corporation, Milford, MA), and an IONPAC® AS15 analytical column (4 x 250 mm, Dionex Corporation, Sunnyvale, CA) with an IONPAC® AG15 guard column. Sulfide was detected using a Coulochem II electrochemical detector (ESA Inc., Chelmsford, MA) equipped with a model 5020 guard cell and a model 5040 amperometric analytical cell with silver target. The applied potentials of the guard cell and analytical cell were 584 and 50 mV, respectively. The output range of the ESA 5040 analytical cell was set at 20 nA/V.
Lung sulfide metabolites were detected by a Dionex CD20 conductivity detector (Dionex Corporation, Sunnyvale, CA). The conductivity detector was equipped with an anion self-regenerating suppressor (ASRS-Ultra 4 mm, Dionex Corporation) in recycle mode. The range of the conductivity detector was 3 µs, and the anion self-regenerating suppressor was set at 300 mA. The data were acquired and integrated by a Baseline 810 chromatography workstation (Waters, Millipore Corporation, Milford, MA).
Analytical-grade reagents were used, and all standards and eluents were prepared using distilled, deionized water with a specific resistance of 17.8 megohm-cm. Sulfide, sulfite, sulfate, and thiosulfate were eluted isocratically at a flow rate of 1.5 ml/min using helium-degassed 28 mM NaOH as the mobile phase. Under these conditions, elution times for sulfide, sulfite, sulfate, and thiosulfate were 4, 8, 10, and 35 min, respectively. Tissue concentrations were determined from the linear regression (r2 = 0.95) of a calibration curve based on aqueous samples within a range of 550 ppb for sulfide and 110 ppm for sulfite, sulfate, and thiosulfate. The assay detection limit for sulfide was 1 ng/ml, corresponding to 0.05 µg/g tissue. Recovery rates for sulfide, sulfite, sulfate, and thiosulfate were 88 ± 5%, 85 ± 5%, 71 ± 10%, and 102 ± 8%, respectively, based on recovery rates obtained from control rat liver samples (n = 35) spiked with known amounts of each analyte of interest.
Statistics.
Unless otherwise noted, data are reported as means ± SEM. All statistical analyses were performed using a standard statistical package (JMP, SAS Institute Inc., Cary, NC). Time-course and dose-response data were evaluated by one-way analysis of variance (ANOVA) followed by a comparison with the preexposure (control) group using Dunnett's test. The distribution of all data was tested for normality using the Shapiro-Wilk test before analysis. Linear regression correlations were performed according to standard statistical procedures and tested by analysis of variance. For all tests, a p value of 0.05 or less was considered significant.
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RESULTS |
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DISCUSSION |
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Hydrogen sulfide is normally present in mammalian tissues, and some evidence suggests that it is required for certain types of nerve transmission (Kimura, 2000). Literature values for endogenous levels of sulfide are variable and depend on the procedures used to extract the sulfide from the tissue and the analytical chemical methods used to quantify this metabolite (Goodwin et al., 1989
; Kage et al., 1988
; Mitchell et al., 1993
). Special care must be taken to minimize the loss of free sulfide from the tissue sample due to the volatility of this gas. We used a strong base (TEAH) not only to digest our tissue samples, but also to minimize evaporative losses of H2S. Another advantage of our analytical method is that the use of an amperometric analytical cell and a conductivity detector allowed us to simultaneously detect and quantify sulfide and sulfide metabolites in the same sample of tissue. Endogenous tissue sulfide concentrations determined with our analytical methods are similar to those reported in the literature. For example, brain sulfide concentrations observed in naive rats (1.21 ± 0.05 µg/g) from our acute study are comparable to values (1.94 ± 0.24 µg/g) reported by Warenycia and coworkers (1990), although the results from our 70-day exposure are somewhat higher. Background lung tissue sulfate concentrations observed in our study (140 ± 6.5 µg/g) were approximately 2.5-fold higher than those observed by Rozman and coworkers (1992).
Our interest in the lung was stimulated by possible portal-of-entry effects associated with H2S inhalation and the known relationship between H2S inhalation and pulmonary edema and fibrinocellular alveolitis (Lopez et al., 1988a). As expected, we observed that end-of-exposure lung sulfide concentrations were highly correlated with the amount of H2S in the exposure atmosphere, and elevated lung sulfide concentrations were observed following a single 3-h H2S exposure to
80 ppm. End-of-exposure lung sulfide concentrations were not increased in rats exposed subchronically to
80 ppm. In contrast, decreased cytochrome oxidase activity was observed in the lung after a 3-h exposure to
30 ppm H2S as well as following subchronic exposure to 80 ppm H2S. This finding indicates that cytochrome oxidase inhibition is a more sensitive biomarker of H2S exposure than tissue sulfide concentrations.
Lung sulfide concentrations rapidly returned to preexposure levels within minutes after the end of a 3-h exposure to 400 ppm H2S, suggesting that rapid pulmonary elimination or metabolism of sulfide occurs. An accumulation of sulfide metabolites was not observed in the lung during the 3-h H2S exposure. Transient increases in lung sulfite, sulfate, and thiosulfate concentrations were observed, however, immediately after the end of the 400-ppm H2S exposure. This increase in sulfide metabolite concentrations occurred coincidentally with the rapid decrease in lung sulfide concentration. This observation suggests that the detoxification of sulfide to sulfate may becomes less effective as the concentration of sulfide increases in blood and other tissues due to H2S exposure (Fischer et al., 2000). A similar pharmacokinetic pattern has been observed in mice exposed to benzene, where competitive inhibition of an intermediate metabolite (phenol) occurs and formation of another metabolite (hydroquinone) is delayed until after the benzene inhalation ends (Medinsky et al., 1996
; Rickert et al., 1979
). Additional studies will be required to confirm our hypothesis that competitive inhibition of sulfide metabolism occurs during H2S inhalation.
We also observed increased sulfide concentrations and cytochrome oxidase inhibition in the upper respiratory tract from H2S-exposed rats. Although our data showed that olfactory, but not respiratory, epithelial sulfide concentrations were significantly elevated following exposure to 400 ppm H2S, the observed differences in end-of-exposure tissue sulfide concentrations are unlikely to be toxicologically significant. For example, end-of-exposure olfactory epithelium sulfide concentrations following a 3-h exposure to 400 ppm H2S were 146% of levels observed in unexposed animals, whereas end-of-exposure respiratory epithelium sulfide concentrations observed in the same animals were 158% of control levels. Cytochrome oxidase activity was significantly decreased within the olfactory and respiratory nasal epithelium immediately after a single 3-h exposure to 30 ppm H2S. Olfactory cytochrome oxidase activity was also significantly decreased to 4566% of control levels following 5 consecutive days of exposure to
30 ppm H2S. Repeated (5-day) H2S exposure did not change cytochrome oxidase activity in the respiratory nasal epithelium. This observation is consistent with our recent studies that showed that regeneration of the nasal respiratory mucosa occurs rapidly during this 5-day period, whereas necrosis of the olfactory mucosa increased in severity (Brenneman et al., 2001). Our data suggest that the regenerated respiratory epithelium becomes resistant to H2S-induced cytochrome oxidase inhibition. It should be noted that our dose-response data for cytochrome oxidase activity in the nasal tissue demonstrates some inconsistencies. For example, H2S-induced inhibition of nasal respiratory epithelial cytochrome oxidase activity was greater in rats exposed to either 30 or 80 ppm than in rats acutely exposed to
200 ppm H2S. This unusual dose-response relationship may indicate that some compensatory changes are occurring in the epithelium in response to H2S exposure. Furthermore, regional differences in sulfide delivery within the olfactory epithelium are correlated with the development of nasal pathology at this site (Moulin et al., 2001). Our sampling procedure does not allow us to detect regional differences in H2S delivery to the olfactory epithelium, as we pooled the entire olfactory epithelium into one sample.
It is reasonable to question whether cytochrome oxidase inhibition is a mode of action for H2S-induced olfactory pathology. Our laboratory has shown that acute inhalation exposure of male rats to 400 ppm H2S results in severe mitochondrial swelling in degenerating olfactory neurons within the olfactory epithelium (Brenneman et al., 2001). This ultrastructural lesion is consistent with, but not specific for, H2S-induced anoxic cell injury due to cytochrome oxidase inhibition. These data provide strong evidence that cytochrome oxidase inhibition may indeed play a critical role in H2S-induced olfactory pathology. When considered together, our data suggest that the olfactory neuroepithelium is intrinsically more sensitive than the nasal respiratory epithelium to H2S-induced cytochrome oxidase inhibition. This result is not unexpected, as neurons are known to be exquisitely sensitive to chemical-induced hypoxic damage (Nicklas et al., 1992).
We did not observe increased hindbrain sulfide concentrations in acutely or subchronically H2S-exposed animals. Warenycia et al. (1989) showed that accumulation of sulfide occurred in the hindbrain of male Sprague-Dawley rats exposed to lethal quantities of sodium hydrosulfide (NaHS), an alkaline salt that liberates H2S in vivo. Our inability to detect an increase in hindbrain sulfide concentrations probably reflected the lower (sublethal) doses of H2S used in our study. We also did not observe altered brain cytochrome oxidase activity in H2S-exposed animals. Savolainen and coworkers (1980) likewise showed that a single 2-h exposure of mice to 100 ppm H2S did not result in inhibition of brain cytochrome oxidase activity. We observed increased liver sulfide concentrations in rats exposed for 3 h to 200 ppm. Despite the presence of elevated liver sulfide concentrations, we did not observe cytochrome oxidase inhibition in this tissue. Indeed, rats exposed to 10 ppm H2S for 3 h had significantly elevated hepatic cytochrome oxidase activity. For example, liver cytochrome oxidase activity was 136% of preexposure levels following a single 3-h exposure to 400 ppm H2S. A similar observation was noted by Khan and coworkers (1998), who also observed a small increase in liver cytochrome oxidase activity (to 109% of control values, not statistically significant) in rats subchronically exposed (8 h/day, 5 days/week, for 5 weeks) to 100 ppm H2S. The biological significance of this observation is unclear, but it implies that respiration in the liver is not inhibited by H2S at these treatment concentrations, and possibly, that H2S detoxification processes in this organ require additional energy demands, as reflected by increased respiratory cytochrome activity.
The results of our study provide important new information defining the relationship between H2S exposure concentration and resulting sulfide concentrations and cytochrome oxidase activities in the hindbrain, lung, and nose, each of which is a critical target for H2S-induced toxicity. Our results suggest that acute exposure to low concentrations ( 30 ppm) of H2S is associated with cytochrome oxidase inhibition in the lung and nose. Inhibition of cytochrome oxidase often occurred in the absence of elevated tissue sulfide concentration. These data suggest that cytochrome oxidase inhibition is a more sensitive biomarker of H2S exposure than is tissue sulfide concentration. It is not unexpected that measurement of total tissue sulfide concentrations is a relatively insensitive biomarker of H2S exposure, as most tissues contain high endogenous levels of sulfide and this metabolite is highly volatile when unbound. More refined studies using radiolabeled H2S with evaluation of total and mitochondrial sulfide could better elucidate the dose-response relationship between tissue sulfide concentration and H2S exposure. Despite the limitations in our experimental design, our data should prove useful in the development of biologically based dosimetry and pharmacodynamic models for this chemical. The development of dosimetry based models should improve the risk assessment for this important environmental contaminant.
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ACKNOWLEDGMENTS |
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NOTES |
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2 Present address: Bristol-Myers Squibb Pharmaceutical Research Institute, PO Box 5400, Princeton, NJ 08543-5400.
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REFERENCES |
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---|
Ammann, H. M. (1986). A new look at physiologic respiratory response to H2S poisoning. J. Hazard. Mater. 13, 369374.[ISI]
Arnold, I. M. F., Dufresne, R. M., Alleyne, B. C., and Stuart, P. J. W. (1985). Health implication of occupational exposures to hydrogen sulfide. J. Occup. Med. 27, 373376.[ISI][Medline]
Bartholomew, T. C., Powell, G. M., Dodgson, K. S., and Curtis, C. G. (1980). Oxidation of sodium sulphide by rat liver, lungs and kidney. Biochem. Pharmacol. 29, 24312437.[ISI][Medline]
Beauchamp, R. O., Jr., Bus, J. S., Popp, J. A., Boreiko, C. J., and Andjelkovich, D. A. (1984). A critical review of the literature on hydrogen sulfide toxicity. Crit. Rev. Toxicol. 13, 2597.[Medline]
Bhambhani, Y. (1999). Acute effects of hydrogen sulfide inhalation in healthy men and women. Environ. Epidemiol. Toxicol. 1, 217230.
Brenneman, K. A., James, R. A., Gross, E. A., and Dorman, D. C. (2000a). Olfactory neuron loss in adult male CD rats following subchronic inhalation exposure to low levels of hydrogen sulfide. Toxicol. Pathol. 28, 326333.[ISI][Medline]
Brenneman, K. A., Wong, B. A., Bucellato, M. A., Costa, E. R., Gross, E. A., and Dorman, D. C. (2000b). Direct olfactory transport of inhaled manganese (54MnCl2) to the rat brain: Toxicokinetic investigations in a unilateral nasal occlusion model. Toxicol. Appl. Pharmacol. 169, 238248.[ISI][Medline]
Brenneman, K. A., Meleason, D. F., Marshall, M. W., James, R. A., Gross, E. A., Martin, J. T., and Dorman, D. C. (in press). Nasal lesions following acute inhalation exposure of male CD rats to hydrogen sulfide: Reversibility and the possible role of regional metabolic capacity in lesion distribution. Toxicol. Pathol.
Buckley, L. A., Morgan, K. T., Swenberg, J. A., James, R. A., Hamm Jr., J. E., and Barrow, C. S. (1985). The toxicity of dimethylamine in F-344 rats and B6C3F1 mice following a 1 year inhalation exposure. Fundam. Appl. Toxicol.5, 341352.[ISI][Medline]
Cannon, W. C., Blanton, E. F., and McDonald, K. E. (1983). The flow-past chamber: An improved nose-only exposure system for rodents. Am. Ind. Hyg. Assoc. J. 44, 923928[ISI][Medline]
Donham, K. J., Knapp, L. W., Monson, R., and Gustafson, K. (1982). Acute toxic exposure to gases from liquid manure. J. Occup. Med. 24, 142145.[ISI][Medline]
Dorman, D. C., Brenneman, K. A., Struve, M. F., Miller, K. L., James, R. A., Marshall, M. W., and Foster, P. M. D. (2000). Fertility and developmental neurotoxicity effects of inhaled hydrogen sulfide in Sprague-Dawley rats. Neurotoxicol. Teratol. 22, 7184.[ISI][Medline]
Fischer, L. J., Gracki, J. A., Long, D. T., Wolff, G. T., and Harrison, K. G. (2000). Health Effects of Low-Level Hydrogen Sulfide in Ambient Air. Report of the Hydrogen Sulfide Investigation Panel, Michigan Environmental Science Board.
Genter, M. B., Owens, D. M., and Deamer, N. J. (1995). Distribution of microsomal epoxide hydrolase and glutathione S-transferase in the rat olfactory mucosa: Relevance to distribution of lesions caused by systemically-administered olfactory toxicants. Chem. Senses 20, 385392.[Abstract]
Goodwin, L. R., Francom, D., Dieken, F. P., Taylor, J. D., Warenycia, M. W., Reiffenstein, R. J., and Dowling, G. (1989). Determination of sulfide in brain tissue by gas dialysis/ion chromatography: Postmortem studies and two case reports. J. Anal. Toxicol. 13, 105109.[ISI][Medline]
Graedel, T. E., Hawkins, D. T., and Claxton, L. D. (1986). Atmospheric Chemical Compounds Sources Occurrence, and Bioassay. Academic Press, New York.
Guidotti, T. L. (1994). Occupational exposure to hydrogen sulfide in the sour gas industry: Some unresolved issues. Int. Arch. Occup. Environ. Health. 66, 153160.[ISI][Medline]
Hall, A. H., and Rumack, B. H. (1997). Hydrogen sulfide poisoning: An antidotal role for sodium nitrite? Vet. Hum. Toxicol. 39, 152154.[ISI][Medline]
Hirsch, A. R., and Zavala, G. (1999). Long-term effects on the olfactory system of exposure to hydrogen sulphide. Occup. Environ. Med. 56, 284287.[Abstract]
Hoidal, C. R., Hall, A. H., Robinson, M. D., Kulig, K., and Rumack, B. H. (1986). Hydrogen sulfide poisoning from toxic inhalations of roofing asphalt fumes. Ann. Emerg. Med. 15, 826830.[ISI][Medline]
Jaakkola, J. J., Vilkka, V., Marttila, O., Jappinen, P., and Haahtela, T. (1990). The South Karelia Air Pollution Study. The effects of malodorous sulfur compounds from pulp mills on respiratory and other symptoms. Am. Rev. Respir. Dis. 142, 134450.[ISI][Medline]
Jiang, X. Z., Buckley, L. A., and Morgan, K. T. (1983). Histopathology of toxic responses to chlorine gas in the nasal passages of rats and mice. Toxicol. Appl. Pharmacol. 103, 143155.
Kage, S., Nagata, T., Kimura, K., and Kudo, K. (1988). Extractive alkylation and gas chromatographic analysis of sulfide. J. Forensic Sci. 33, 21722.[ISI][Medline]
Kage, S., Nagata, T. Takekawa, K., Kimura, K., Kudo, K., and Imamura, T. (1992). The usefulness of thiosulfate as an indicator of hydrogen sulfide poisoning in forensic toxicological examination: A study with animal experiments. Jpn. J. Forensic Toxicol. 10, 223227.
Kangas, J., and Savolainen, H. (1987). Urinary thiosulphate as an indicator of exposure to hydrogen sulphide vapour. Clin. Chim. Acta. 164, 710.[ISI][Medline]
Khan, A. A., Coppock, R. W., Schuler, M. M., and Prior, M. G. (1998). Biochemical effects of subchronic repeated exposures to low and moderate concentrations of hydrogen sulfide in Fischer 344 rats. Inhal. Toxicol. 11, 10371044.
Khan, A. A., Schuler, M. M., Prior, M. G., Yong, S., Coppock, R. W., Florence, L. Z., and Lillie, L. E. (1990). Effects of hydrogen sulfide exposure on lung mitochondrial respiratory chain enzymes in rats. Toxicol. Appl. Pharmacol. 103, 482490.[ISI][Medline]
Kilburn, K. H. (1993). Case report: Profound neurobehavioral deficits in an oil field worker overcome by hydrogen sulfide. Am. J. Med. Sci. 306, 301305.[ISI][Medline]
Kilburn, K. H. (1997). Exposure to reduced sulfur gases impairs neurobehavioral function. South. Med. J. 90, 9971006.[ISI][Medline]
Kimura, H. (2000). Hydrogen sulfide induces cyclic AMP and modulates NMDA receptor. Biochem. Biophys. Res. Commun. 267, 129133.[ISI][Medline]
Lopez, A., Prior, M., Lillie, L. E., Gulayets, C., and Atwal, O. S. (1988a). Histologic and ultrastructural alterations in lungs of rats exposed to sub-lethal concentrations of hydrogen sulfide. Vet. Pathol. 25, 376384.[Abstract]
Lopez, A., Prior, M., Yong, S., Lillie, L., and Lefebvre, M. (1988b). Nasal lesions in rats exposed to hydrogen sulfide for four hours. Am. J. Vet. Res. 49, 11071111.[ISI][Medline]
Medinsky, M. A., Kenyon, E. M., Seaton, M. J., and Schlosser, P. M. (1996). Mechanistic considerations in benzene physiological model development. Environ. Health Perspect. 104(Suppl.), 13991404[ISI][Medline]
Mitchell, T. W., Savage, J. C., and Gould, D. H. (1993). High-performance liquid chromatography detection of sulfide in tissues from sulfide-treated mice. J. Appl. Toxicol. 13, 389394.[ISI][Medline]
Morgan, K. T. (1991). Approaches to the identification and recording of nasal lesions in toxicology studies. Toxicol. Pathol. 19, 337351.[ISI][Medline]
Morgan, K. T., and Monticello, T. M. (1990). Airflow, gas deposition, and lesion distribution in the nasal passages. Environ. Health Perspect. 85, 209218.[ISI][Medline]
Moulin, F. J. M., Brenneman, K. A., Kimbell, J. S., James, R. A., and Dorman, D. C. (in press). Predicted regional flux of hydrogen sulfide correlates with distribution of nasal olfactory lesions in rats. Toxicol. Sci.
NRC (1996). Guide for the Care and Use of Laboratory Animals. National Research Council, National Academy Press, Washington, DC.
Nicholls, P., and Kim, J. K. (1982). Sulphide as an inhibitor and electron donor for the cytochrome c oxidase system. Can. J. Biochem. 60, 613623.[ISI][Medline]
Nicklas, W. J., Saporito, M., Basma, A., Geller, H. M., and Heikkila, R. E. (1992). Mitochondrial mechanisms of neurotoxicity. Ann. N.Y Acad. Sci. 648, 2836.[ISI][Medline]
Reiffenstein, R. J., Hulbert, W. C., and Roth, S. H. (1992). Toxicology of hydrogen sulfide. Ann. Rev. Pharmacol. Toxicol. 32, 109134.[ISI][Medline]
Rickert, D. E., Baker, T. S., Bus, J. S., Barrow, C. S., and Irons, R. D. (1979). Benzene disposition in the rat after exposure by inhalation. Toxicol. Appl. Pharmacol. 49, 417423.[ISI][Medline]
Rocklin, R. D. and Johnson, E. L. (1983). Determination of cyanide, sulfide, iodide, and bromide by ion chromatography with electrochemical detection. Anal. Chem. 55, 47.[ISI]
Rozman, P., Kim, H. J., Madhu, C., and Klaassen, C. D. (1992). Tissue sulfate determination by ion chromatography. J. Chromatogr. 574, 146149.[Medline]
Savolainen, H., Tenhunen, R., Elovaara, E., and Tossavainen, A. (1980). Cumulative biochemical effects of repeated subclinical hydrogen sulfide intoxication in mouse brain. Int. Arch. Occup. Environ. Health 46, 8792.[ISI][Medline]
Struve, M. F., Brisbois, J. N., James, R. A., Marshall, M. W., and Dorman, D. C. (2001). Behavioral and neurochemical effects of short-term exposure to hydrogen sulfide in Sprague Dawley rats. Neurotoxicology 22, 375385.[ISI][Medline]
Warenycia, M. W., Goodwin, L. R., Benishin, C. G., Reiffenstein, R. J., Francom, D. M., Taylor, J. D., and Dieken, F. P. (1989). Acute hydrogen sulfide poisoning. Demonstration of selective uptake of sulfide by the brainstem by measurement of brain sulfide levels. Biochem. Pharmacol. 38, 973981.[ISI][Medline]
Warenycia, M. W., Goodwin, L. R., Francom, D. M., Dieken, F. P., Kombian, S. B., and Reiffenstein, R. J. (1990). Dithiothreitol liberates non-acid labile sulfide from brain tissue of H2S-poisoned animals. Arch. Toxicol. 64, 650655.[ISI][Medline]
Warneck, P. (1988). Chemistry of the Natural Atmosphere. Academic Press, New York.
Watt, M. M., Watt, S. J., and Seaton, A. (1997). Episode of toxic gas exposure in sewer workers. Occup. Environ. Med. 54, 277280.[Abstract]
Weyant, R. S., Chan, W. C., and Austin, G. E. (1988). Automated marker enzyme analysis of density gradient fractions using the Cobas-Bio® centrifugal analyzer. Am. J. Clin. Pathol. 89, 384389.[ISI][Medline]