Reproductive toxicity of 2-bromopropane in Sprague Dawley rats

Carcinogenicity and testicular toxicity of 2-bromopropane in a 26-week inhalation study using the rasH2 mouse model

2-Bromopropane (2-BP) is a colorless liquid at room temperature and is used in closed systems in factories, mainly as an intermediate for medicines, pesticides, and other chemicals. However, the carcinogenicity of 2-BP is still unknown. The CByB6F1-Tg(HRAS)2Jic (rasH2) transgenic mouse model has been established as an alternative to long-term studies (1.5 years-lifetime) to detect carcinogenicity in as short a time as six months. We performed a 26-week inhalation exposure study of 2-BP using the rasH2 mouse model. Male and female rasH2 mice were exposed to 0, 67, 200, or 600 ppm of 2-BP for 6 h/day, 5 days/week for 26 weeks. All tissues and blood were collected and subjected to biological and histopathological analyses. The results showed a concentration-dependent increase in lung tumor development in male and female rasH2 mice exposed by inhalation to 2-BP, which was significant by Peto's and Poly-3 trend tests. Furthermore, in male rasH2 mice, 2-BP was found to be a testicular toxin. This study is the first to demonstrate that 2-BP is carcinogenic in male and female mice and a testicular toxin in male mice using the rasH2 mouse model.

Assessing reproductive toxicity of two environmental toxicants with a novel in vitro human spermatogenic model

Environmental influences and insults by reproductive toxicant exposure can lead to impaired spermatogenesis or infertility. Understanding how toxicants disrupt spermatogenesis is critical for determining how environmental factors contribute to impaired fertility. While current animal models are available, understanding of the reproductive toxic effects on human fertility requires a more robust model system. We recently demonstrated that human pluripotent stem cells can differentiate into spermatogonial stem cells/spermatogonia, primary and secondary spermatocytes, and haploid spermatids; a model that mimics many aspects of human spermatogenesis. Here, using this model system, we examine the effects of 2-bromopropane (2-BP) and 1,2,dibromo-3-chloropropane (DBCP) on in vitro human spermatogenesis. 2-BP and DBCP are non-endocrine disrupting toxicants that are known to impact male fertility. We show that acute treatment with either 2-BP or DBCP induces a reduction in germ cell viability through apoptosis. 2-BP and DBCP affect viability of different cell populations as 2-BP primarily reduces spermatocyte viability, whereas DBCP exerts a much greater effect on spermatogonia. Acute treatment with 2-BP or DBCP also reduces the percentage of haploid spermatids. Both 2-BP and DBCP induce reactive oxygen species (ROS) formation leading to an oxidized cellular environment. Taken together, these results suggest that acute exposure with 2-BP or DBCP causes human germ cell death in vitro by inducing ROS formation. This system represents a unique platform for assessing human reproductive toxicity potential of various environmental toxicants in a rapid, efficient, and unbiased format.

Occupational exposure to neurotoxic substances in Asian countries - challenges and approaches

The fact that a conference on neurotoxicity was held in China triggered the idea to provide an insight into occupational diseases, their development and the approaches to investigate them in Asian countries. A historical review, a meta-analysis, and studies on humans and animals provide impressions on past and current problems. The Korean example showed that each newly introduced industry is accompanied by its own problems as regards occupational diseases. Mercury and carbon disulfide were of importance in the beginning, whereas solvents and manganese became important later. Outbreaks of diseases were important reasons to guide both the public and the governmental attention to prevention and allowed within a relatively short time considerable progress. As the example on the replacement of 2-bromopropane by 1-bromopropane showed, also the introduction of chemicals that are more beneficial for the environment may result in additional occupational risks. A lower mutagenicity of 1-bromopopane was shown to be associated with a greater neurotoxicity in Japanese studies. Although occupational health and diseases are commonly related to adults, child workers exposed to solvents were examined in a Lebanese study. The study started outlining the health hazards in young workers because they might be at a much greater risk due to the not yet completed maturation of their nervous system. That some occupational diseases are not yet a focus of prevention was shown by the study on pesticides. If at all, the serious health consequences resulting from excessive exposure were investigated. Research enabling precautionary actions was not available from the international literature. Despite globalization the knowledge on occupational diseases is not yet "globalized" and each country obviously undergoes its own development triggered by local experiences. Economic development that requires a healthy workforce, but also public interest that challenges governmental regulations further efforts on the prevention of occupational diseases. The paper reflects a summary of the talks presented at the symposium "Occupational Neurotoxicities in Asian Countries" as part of the 11th International Symposium on Neurobehavioral Methods and Effects in Occupational and Environmental Health.

Occupational reproductive function abnormalities and bladder cancer in Korea

The purpose of this study was to review occupational reproductive abnormalities and occupational bladder cancer in Korea and to discuss their toxicological implications. Reproductive dysfunction as a result of 2-bromopropane poisoning was first reported in Korean workers. In 1995, 23 of the 33 workers (25 female and 8 male workers) who were exposed to 2-bromopropane during the assembly of tactile switch parts developed reproductive and/or hematopoietic disorders. A total of 17 (68%) workers were diagnosed with ovarian failure. Two of the eight male workers experienced azoospermia and four workers experienced some degree of oligospermia or reduced sperm motility. In summary, 2-bromopropane poisoning caused severe reproductive effects in Korean workers. The prognosis was poor for reproductive dysfunction. A few cases of occupational bladder cancer have been reported in Korea, whereas other cancers of the urinary tract have not been reported after occupational exposure. A few cases of benzidine-induced cancer have been reported in Korea and 592 workers in Japan have received compensation for benzidine and β-naphthylamine-induced cancer. In conclusion, a few cases of benzidine-induced occupational bladder cancer have been reported in Korea. However, benzidine-induced bladder cancer will likely be an important occupational health issue in Korea in the coming years.

Whole-body inhalation exposure to 1-bromopropane suppresses the IgM response to sheep red blood cells in female B6C3F1 mice and Fisher 344/N rats

1-Bromopropane (1-BP) is categorized as a high-production-volume chemical and is currently used in the manufacture of pharmaceuticals, pesticides, and other chemicals. Its usage is estimated to be around 5 million pounds per year, resulting in the potential for widespread exposure in the workplace. Case reports and animal studies have suggested exposure to this compound may cause adverse reproductive and neurological effects. Using a battery of immunological assays, the immunotoxicity of 1-BP after whole body inhalation exposure in both mice and rats was evaluated. Significant decreases in the spleen immunoglobulin (Ig) M response to sheep red blood cells (SRBC) were observed in both mice (125-500 ppm) and rats (1000 ppm) after exposure to 1-BP for 10 wk. In addition, total spleen cells and T cells were significantly decreased after approximately 4 wk of 1-BP exposure in both mice (125-500 ppm) and rats (1000 ppm). No change in natural killer (NK) cell activity was observed. The observed alterations in spleen cellularity, phenotypic subsets, and impairment of humoral immune function across species raise further concern about human exposure to 1-BP and demonstrate the need for additional investigations into potential adverse health effects.

Transfer of occupational health problems from a developed to a developing country: lessons from the Japan-South Korea experience

Many corporations move their manufacturing facilities or technologies from developed to developing countries. Stringent regulations have made it costly for industries to operate in developed, industrialized countries. In addition, labor costs are high in these countries, and there is increasing awareness among the general public of the health risks associated with industry. The relocation of hazardous industries to developing countries is driven by economic considerations: high unemployment, a cheaper labor force, lack of regulation, and poor enforcement of any existing regulations make certain countries attractive to business. The transfer of certain industries from Japan to Korea has also brought both documented occupational diseases and a new occupational disease caused by chemicals without established toxicities. Typical examples of documented occupational diseases are carbon disulfide poisoning in the rayon manufacturing industry, bladder cancer in the benzidine industry, and mesothelioma in the asbestos industry. A new occupational disease due to a chemical without established toxicities is 2-bromopropane poisoning. These examples suggest that counter-measures are needed to prevent the transfer of occupational health problems from a developed to a developing country. Corporate social responsibility should be emphasized, close inter-governmental collaboration is necessary and cooperation among non-governmental organizations is helpful.

Reversibility of the Adverse Effects of 1-Bromopropane Exposure in Rats

Previous experiments indicated that 1-bromopropane (1-BP), an alternative to chloroflurocarbons, is neurotoxic and inhibits spermiation in the testis. Here we investigated the reversibility of the toxic effects of 1-BP in rats. Male Wistar rats were divided into three equal groups of 24 each and exposed by inhalation to 0, 400 or 1000 ppm of 1-BP for 6 weeks (8 hrs/day, 7 days/week). Eight rats from each group were sacrificed at the end of 6 weeks exposure, and at 4 and 14 weeks after the end of exposure, to assess the recovery processes. We studied sperm count, motility, morphology and testicular histopathology, as well as blood pressure, skin temperature and hindlimb muscle strength. At the end of 6 weeks of exposure to 1000 ppm (0 week recovery), testicular weight, epididymal weight, sperm count and motility were low, morphologically abnormal sperm were increased and spermatogenic cells showed diffuse degeneration. These changes did not show full recovery at 14 weeks recovery, with the exception of the prostate and seminal vesicular weights, which recovered back to control values. At 400 ppm, increased retained spermatids at 0 week recovery returned to normal at 4 weeks recovery. Exposure to 1000 ppm produced sustained reduction of hindlimb muscle strength at 14 weeks recovery, whereas normalization of the skin temperature and blood pressure was noted after transient changes. Our study showed that the effect of 1-BP on spermatogenesis is dose-dependent; low exposure inhibited spermiation and hormone-dependent organ weight reduction and these changes were transient, while a higher dose of 1000 ppm 1-BP caused persistent depletion of spermatogenic cells.

DNA damage in leukocytes of workers occupationally exposed to 1-bromopropane

1-bromopropane (1-BP; n-propyl bromide) (CAS No. 106-94-5) is an alternative to ozone-depleting chlorofluorocarbons that has a variety of potential applications as a degreasing agent for metals and electronics, and as a solvent vehicle for spray adhesives. Its isomer, 2-brompropane (2-BP; isopropyl bromide) (CAS No. 75-26-3) impairs antioxidant cellular defenses, enhances lipid peroxidation, and causes DNA damage in vitro. The present study had two aims. The first was to assess DNA damage in human leukocytes exposed in vitro to 1- or 2-BP. DNA damage was also assessed in peripheral leukocytes from workers with occupational exposure to 1-BP. In the latter assessment, start-of- and end-of-work week blood and urine samples were collected from 41 and 22 workers at two facilities where 1-BP was used as a solvent for spray adhesives in foam cushion fabrication. Exposure to 1-BP was assessed from personal-breathing zone samples collected for 1-3 days up to 8h per day for calculation of 8h time weighted average (TWA) 1-BP concentrations. Bromide (Br) was measured in blood and urine as a biomarker of exposure. Overall, 1-BP TWA concentrations ranged from 0.2 to 271 parts per million (ppm) at facility A, and from 4 to 27 ppm at facility B. The highest exposures were to workers classified as sprayers. 1-BP TWA concentrations were statistically significantly correlated with blood and urine Br concentrations. The comet assay was used to estimate DNA damage. In vitro, 1- or 2-BP induced a statistically significant increase in DNA damage at 1mM. In 1-BP exposed workers, start-of- and end-of-workweek comet endpoints were stratified based on job classification. There were no significant differences in DNA damage in leukocytes between workers classified as sprayers (high 1-BP exposure) and those classified as non-sprayers (low 1-BP exposure). At the facility with the high exposures, comparison of end-of-week values with start-of-week values using paired analysis revealed non-sprayers had significantly increased comet tail moments, and sprayers had significantly increased comet tail moment dispersion coefficients. A multivariate analysis included combining the data sets from both facilities, log transformation of 1-BP exposure indices, and the use of multiple linear regression models for each combination of DNA damage and exposure indices including exposure quartiles. The covariates were gender, age, smoking status, facility, and glutathione S-transferase M1 and T1 (GSTM1, GSTT1) polymorphisms. In the regression models, start-of-week comet tail moment in leukocytes was significantly associated with serum Br quartiles. End-of-week comet tail moment was significantly associated with 1-BP TWA quartiles, and serum Br quartiles. Gender, facility, and GSTM1 had a significant effect in one or more models. Additional associations were not identified from assessment of dispersion coefficients. In vitro and in vivo results provide limited evidence that 1-BP exposure may pose a small risk for increasing DNA damage.

Neuro-reproductive toxicities of 1-bromopropane and 2-bromopropane

2-Bromopropane was used as an alternative to chlorofluorocarbons in a Korean electronics factory and caused reproductive and hematopoietic disorders in male and female workers. This causality was revealed by animal studies, and target cells were identified in subsequent studies. After identification of 2-bromopropane toxicity, 1-bromopropane was introduced to the workplace as a new alternative to ozone-depleting solvents. 1-Bromopropane was considered less mutagenic than 2-bromopropane, but, in contrast, animal experiments revealed that 1-bromopropane is a potent neurotoxic compound compared with 2-bromopropane. It was also revealed that 1-bromopropane has reproductive toxicity, but the target cells are different from those of 2-bromopropane. Exposure to 1-bromopropane inhibits spermiation in male rats and disrupts the development of follicles in female rats, in contrast to 2-bromopropane, which targets spermatogonia and oocytes in primordial follicles. After the first animal study describing the neurotoxicity of 1-bromopropane, human cases were reported. Those cases showed decreased sensation of vibration and perception, paresthesia in the lower extremities, decreased sensation in the ventral aspects of the thighs and gluteal regions, stumbling and headache, as well as mucosal irritation, as the initial symptoms. The dose-response of bromopropanes in humans and mechanism(s) underlying the differences in the toxic effects of the two bromopropanes remain to be determined.

Occupational Exposure Associated with Reproductive Dysfunction

Evidence suggestive of harmful effects of occupational exposure on the reproductive system and related outcomes has gradually accumulated in recent decades, and is further compounded by persistent environmental endocrine disruptive chemicals. These chemicals have been found to interfere with the function of the endocrine system, which is responsible for growth, sexual development and many other essential physiological functions. A number of occupations are being reported to be associated with reproductive dysfunction in males as well as in females. Generally, occupations involving the manufacture/or application of some of the persistent chemicals that are not easily degradable as well as bio-accumulative chemicals, occupations involving intensive exposure to heat and radiation, occupations involving the use of toxic solvents as well as toxic fumes are reported to be associated with reproductive dysfunction. Occupational exposure of males to various persistent chemicals have been reported to have male mediated adverse reproductive outcomes in the form of abortion, reduction in fertility etc. with inconclusive or limited evidence. Nevertheless, there is a need for more well designed studies in order to implicate any individual chemical having such effects as in most occupations workers are exposed to raw, intermediate and finished products and there are also several confounding factors associated with lifestyles responsible for reproductive dysfunction. There is an urgent need to look at indiscriminate use of persistent chemicals especially pesticides and persistent organic pollutants (POP's) as these chemicals enter the food chain also and could be potential for exposure during the critical period of development. It is also necessary to impart information, and to educate about the safe use of these chemicals, as a very sensitive reproduction issue is involved with exposure to these chemicals. Occupational exposures often are higher than environmental exposures, so that epidemiological studies should be conducted on these chemicals, on a priority basis, which are reported to have adverse effects on reproduction in the experimental system.

A survey on exposure level, health status, and biomarkers in workers exposed to 1-bromopropane

BACKGROUND

The aim of this study was to evaluate the health effects of exposure mainly to 1-bromopropane, which is an alternative to ozone-depleting solvents, and to establish biomarkers for assessing 1-bromopropane exposure.

METHODS

Twenty-four female and 13 male workers of a 1-bromopropane-factory were interviewed, and their urine and blood samples were collected. Measured parameters included 1-bromopropane levels in the factory, as well as individual exposure levels, urinary 1-bromopropane levels, enzymatic activity and M subunit's concentration of serum creatine kinase (CK).

RESULTS

Frequent symptoms reported by workers exposed to 1-bromopropane were nose, throat, and eyes irritation or malaise and/or headache. Urinary 1-bromopropane levels correlated significantly with individual exposure levels, but enzymatic activity or CK-M subunit did not.

CONCLUSIONS

The symptoms suggested irritation of the mucous membrane and possible adverse effects on the central nervous system. There were no severe chronic symptoms suggestive of neurological damage in workers exposed to less than 170 ppm. Urinary 1-bromopropane level may be a good indicator of exposure. Am. J. Ind. Med. 45:63-75, 2004.

Acute effects of 2-bromopropane and 1,2-dibromopropane on hepatotoxic and immunotoxic parameters in female BALB/c mice

In the present studies, the acute toxic effects of 2-bromopropane (2-BP) and its analog, 1,2-dibromopropane (1,2-DBP), were investigated in female BALB/c mice. The mice were treated orally with either 2-BP at 2000 and 4000 mg/kg or 1,2-DBP at 300 and 600 mg/kg. Four days before necropsy, the mice were immunized intraperitoneally with sheep red blood cells (SRBCs). 1,2-DBP reduced the weights of the spleen and thymus weights and decreased the number of splenic cells. In addition, treatment with 1,2-DBP suppressed the antibody response to SRBCs. Meanwhile, only the antibody response was significantly suppressed by treatment with 2-BP. In the subsequent studies, the time course effects of 2-BP and 1,2-DBP on the hepatotoxic parameters were compared in female BALB/c mice. When mice were treated orally with either one of these chemicals for 6, 12, 24 and 48 h, the activities of serum alanine aminotransferase and aspartate aminotransferase elevated significantly only with 1,2-DBP 24 h after the treatment. The hepatic content of glutathione was reduced by 1,2-DBP. Meanwhile, these parameters were increased by 2-BP. The present results suggest that 1,2-DBP in the Solvent 5200 also contributes to the immnunotoxicity, although 2-BP is a major component.

A histopathologic study of the nervous system after inhalation exposure of 1-bromopropane in rat

1-Bromopropane (1-BP) has recently become known as an alternative cleaning material with less damage to the ozone layer. However, its toxicity is not fully evaluated. This study was designed to investigate the repeated inhalation toxicity of 1-BP on the nervous systems in Sprague-Dawley rats. The experiment was done by repeated exposure of the rats to 0, 200, 500, and 1250 ppm for 6 h per day, 5 days a week, for 13 weeks, respectively. Morphologic studies were done for the central nervous system, sacral and peroneal nerves. The serial sections of the brain and spinal cord of 1-BP inhalation groups revealed no pathological features either in the gray or white matter. The nerve fiber teasing, light and electron microscopic studies of the sacral and peroneal nerve fibers showed no significant difference between 1-BP inhalation groups and the control group. From these results, it is concluded that the nervous system is histologically resistant to the repeated inhalation of 1-BP up to 1250 ppm for 13 weeks. Experiments with higher concentrations of 1-BP and the functional studies are necessary to clarify the 1-BP toxicity.

Impairment of male rat reproductive function in F1 offspring from dams exposed to 2-bromopropane during gestation and lactation

The toxic effects of 2-bromopropane (2-BP) on the reproductive tracts of male F1 offspring from dams exposed to 2-BP during gestation and lactation were investigated. Ten pregnant (sperm-positive) Sprague-Dawley rats per group were exposed sc to 2-BP at 135, 405, and 1215 mg/kg/day from gestation day (GD) 6 to postnatal day (PND) 20. 2-BP decreased the proportion of dams littering at the two highest doses. At the highest dose, the rate of delivery and surviving pups were significantly lower than in the controls (P < or = 0.05). The relative weights of testes vs. brain were significantly lower than the controls (P < or = 0.05) on PND 33 and 63 at 405 mg/kg/day, and on PND 90 at 1215 mg/kg/day in the F1 rats. Seminiferous tubule atrophy, germ cell loss, and increased Leydig cell proliferation were observed at the highest dose by histopathologic examination. Female offspring has a decrease in all follicle types at the high dose. These results suggest that gestational and lactational exposure to 2-BP at a high maternally toxic dose impairs the development of the reproductive organs of the offspring.

Immunotoxic effects of 2-bromopropane in male Sprague-Dawley rats: a 28-day exposure study

Immunotoxic effects of 2-bromopropane were investigated in male Sprague-Dawley rats. The rats were treated orally daily with 2-bromopropane at 100, 330, or 1000 mg/kg for 28 consecutive days. Four days before necropsy, the rats were immunized intravenously with sheep red blood cells (SRBCs). The body and thymus weights were significantly reduced by treatment with 2-bromopropane at the highest dose. In addition, the numbers of splenic and thymic cells were decreased by 2-bromopropane. In hematology, the numbers of white blood cells, red blood cells, and platelets were significantly reduced. Among the serum clinical parameters, the levels of chloride ion were significantly increased by 2-bromopropane. The antibody response to SRBCs was significantly suppressed at the highest dose. With immunized animals, immunophenotyping of splenic and thymic cells was performed to investigate the changes of the number of macrophages, B cells, and T cells in spleen and the number of CD4+ and CD8+ cells in thymus. The numbers of most cell types were significantly decreased in the spleen when animals were treated with 2-bromopropane at 1,000 mg/kg. Likewise, all cell types of thymus were significantly decreased by 2-bromopropane. The present results suggest that 2-bromopropane may have an immunotoxic potential in male Sprague-Dawley rats when the rats are exposed for 28 d.

Synthesis, characterization and in vtro identification of N7-guanine adduct of 2-bromopropane

Recently, we have reported that 2-bromopropane might have an immunotoxic potential in rats when exposed for 28 days. In the present studies, the possibility of 2i-deoxyguanosine adduct formation by 2-bromopropane was investigated in vitro to elucidate molecular mechanism of 2-bromopropane-induced immunosuppression. N7-Guanine adduct of 2'-bromopropane (i.e., N7-isopropyl guanine) was chemically synthesized and structurally characterized by analysis of UV, 1H-NMR, '3C-NMR, COSY and fast atom bombardment mass spectrometry to use as a reference material. Incubation of 2'-deoxyguanosine with an excess amount of 2-bromopropane in PBS buffer solution, pH 7.4, at 37 degrees C for 16 h, followed by a thermal hydrolysis, produced a detectable amount of N7-isopropyl guanine by an HPLC and UV analysis. The present results suggest that 2-bromopropane might form a DNA adduct in N7 position of 2'-deoxyguanosine at a physiological condition.

Effects of 1-bromopropane, 2-bromopropane, and 1,2-dichloropropane on the estrous cycle and ovulation in F344 rats

The present study was performed to investigate comparatively the toxic effects of inhalation exposure of 1-bromopropane, 2-bromopropane, and 1,2-dichloropropane on reproductive physiology, particularly on the estrous cycle and spontaneous ovulation in female F344 rats. The rats received inhalation exposure to different halogenated propanes, and were exposed daily for 8 h throughout almost 3 weeks to 0,50,200 and 1000 ppm of 1-bromopropane or 2-bromopropane, or to 0,50,100 and 200 ppm of 1,2-dichloropropane. Throughout the exposure period of 1-bromopropane or 2-bromopropane, the ratio of the number of estrous cycle of 6 days or longer to the number of all cycles in both 1000 ppm groups were about two-fold the ratio in each control group, however, no significant difference was found between the ratios of exposed and control groups. The ratios of such long estrous cycles in groups exposed to 100 or 200 ppm of 1,2-dichloropropane were six- to seven-fold higher than that of the control group. These ratios in exposed rats differed significantly from those of controls. The number of ovulated ova in rats exposed to 1,2-dichloropropane decreased in a dose-dependent manner, and the number of ovulated ova in the 200 ppm group was significantly different from that of control rats. Such significant changes in ovulation were not observed in rats exposed to 1-bromopropane or 2-bromopropane. The absolute and relative weights of the ovaries and uterus in rats exposed to three halogenated propanes were not significantly different from those in each control. Therefore, the present study clarified that: (1) 1,2-dichloropropane prolonged the length of the estrous cycle and inhibited spontaneous ovulation in F344 rats; and (2) the potency of 1,2-dichloropropane to disturb the female reproductive physiology appeared to be greater compared with that of 1-bromopropane and 2-bromopropane under the present conditions of inhalation exposure.

Involvement of Bcl-2 family genes and Fas signaling system in primary and secondary male germ cell apoptosis induced by 2-bromopropane in rat

Epidemiological surveys and animal experimental studies suggest that exposure to 2-bromopropane (2-BP) could result in reproductive and hematopoietic disorders. The objectives of this study were to investigate the role of apoptosis in 2-BP-induced testicular toxicity and whether this process involves Bcl-2 family genes and the Fas signaling system. Rats were injected percutaneously with 1350 mg/kg 2-BP for 1 to 5 days and then were euthanized at 6 or 12 h after one dose, 6 h after two, three, or five doses, and 2 or 9 days after the final treatment. Light and electron microscopic analyses, TUNEL staining of DNA fragments, agarose gel electrophoresis of low-molecular-weight DNA, and Western blotting analysis of Bcl-2 family proteins and Fas receptor and ligand were conducted. Two-day treatment resulted in selective degeneration of spermatogonia with marked nuclear chromatin condensation. DNA ladder formation on the agarose gel further validated the findings of TUNEL-stained apoptotic cells. The percentage of apoptotic-positive tubules and apoptotic cell index increased time dependently. 2-BP treatment resulted in two distinct morphological changes: an immediate effect on spermatogonia and secondary apoptosis of spermatocytes 9 days after treatment. Downregulation of Bcl-2 after the first or second injection of 2-BP and upregulation of Bax after the first treatment contributed to the initiation of primary apoptosis of spermatogonia. Expression of FasL was inhibited while expression of Fas increased after the 2-BP treatment and remained at levels about two times of the control. However, it increased about sixfold of the control by day 9 after final injection, which contributed to the induction of secondary apoptosis of spermatocytes. Our results indicate that 2-BP resulted in apoptotic death of testicular germ cells and that this process involves the Bcl-2 family genes and the Fas signaling system.

2-Bromopropane induced germ cell apoptosis during spermatogenesis in male rat

2-Bromopropane (2-BP) causes testicular toxicity in humans and rats. However, the germ cell degeneration of testicular toxicity by 2-BP has not been understood. 2-BP at doses of 135, 405, and 1,355 mg/kg/day was daily injected subcutaneously into Sprague-Dawley rats for 28 days. At the dose of 1,355 mg/kg/day, 2-BP significantly decreased the weights of body and testes, eipididymis, seminal vesicle, and prostate, as well as daily sperm production. Atrophy of seminiferous tubules accompanied with degeneration of germ cells such as spermatogonia, spermatocytes, and elongated spermatids was observed in the testes of rats exposed to the 405 mg/kg/day and 1,355 mg/kg/day of 2-BP. TUNEL-positive germ cells were appeared in the 405 and 1,355 mg/kg/day of 2-BP-treated groups. In addition, ultrastructure alterations of apoptotic germ cells were observed by the electron microscopy study. Dead elongated spermatids were observed at 1,355 mg/kg/day after 28 days exposure. These results suggest that 2-BP impair spermatogenesis may result from apoptotic germ cell death.

Influence of 2-bromopropane on reproductive system--short-term administration of 2-bromopropane inhibits ovulation in F344 rats

The present study was performed to investigate the toxic effects of 2-bromopropane (2BP) on the female reproductive system. Female F344 rats were administered 2BP (500 or 1000 mg/kg, i.p.) at intervals of 2 or 3 days for 15-17 days. The body weights were measured and estrous stages were observed throughout the experimental period. Ovulation, organ weights, ovarian histology, and blood biochemistry were investigated on the terminal day of the experiment. Uterine weights in rats treated with 2BP were significantly lower than those in control animals. Body, liver, kidney, and adrenal weights in 2BP-treated rats showed no significant differences from control values. 2BP treatment prolonged estrous cycles and decreased the number of ovulated ova in spontaneous ovulation. In addition, histological examinations showed that the preovulatory follicles in the ovary were altered markedly in 2BP groups. These results show that even in short-term treatment, 2BP injured the ovary, particularly the preovulatory follicles. It appears that these damages of the preovulatory follicles induced by 2BP reduced the numbers of spontaneously ovulated ova in female F344 rats.

Occupational health survey on workers exposed to 2-bromopropane at low concentrations

BACKGROUND

Recent case studies in Korea and animal studies revealed the reproductive and hematopoietic toxicity of 2-bromopropane introduced into workplaces as an alternative to ozone-layer depleting chlorofluorocarbons. We aimed to clarify the dose-effect relationship of 2-bromopropane in workers.

METHOD

The exposure concentration of 2-bromopropane and hematological indices, hormonal levels, menstruation status, and sperm indices were examined in 25 workers (11 males, 14 females) at a 2-bromopropane factory. Regression analyses of the examined indices against time-weighted average (TWA) of exposure concentration were conducted.

RESULTS

Amenorrhea or polymenorrhea was observed only in older females. Hematological indices had a significant relation with TWA of exposure concentration in females with normal menstruation. However, no other indices showed any significant relation with TWA of 2-bromopropane.

CONCLUSIONS

No severe cases of reproductive or hematopoietic disorders were found at less than 10 ppm (TWA), but a possible adverse effect of 2-bromopropane on hematopoiesis could not be disproved.

Histopathological evidence that spermatogonia are the target cells of 2-bromopropane

To confirm the target cell of 2-bromopropane within the testis, 1355 mg/kg of 2-bromopropane was subcutaneously injected to rats for 1-5 days and the numbers of spermatogonia and spermatocytes were examined 6 h after each last injection. The number of stage I spermatogonia decreased after the first 2-bromopropane injection and the number of spermatogonia at the other stages also decreased following repetitive injection. The number of these spermatogonia decreased further by the repetition of 2-bromopropane injection. In addition, the delay in mitotic division of type B spermatogonia was frequently observed after the fifth 2-bromopropane injection. The number of stage I pachytene spermatocytes also decreased slightly after the first 2-bromopropane injection, although it did not decrease further following repetitive injection. Therefore, we concluded that spermatogonia are the target cells of 2-bromopropane in rats.