Influence of strain and age on the induction of mammary tumours by diethylstilboestrol in C3H mice

C3H/HeJ and C3H/HeN female mice were fed diets containing targeted concentrations of 320 or 640 ppb diethylstilboestrol (DES) starting at 7 or 11 wk of age and continuing throughout their remaining lifespan. Regardless of the DES concentration there was a faster rate of development and higher final incidence of mammary adenocarcinomas among the C3H/HeN mice than among the C3H/HeJ mice. In C3H/HeN mice started on DES when 11 wk old, mammary tumours developed more rapidly than when treatment was started at 7 wk of age. This was also true for C3H/HeJ mice given 320 ppb DES but not for those treated with 640 ppb DES. Both age at the start of treatment and strain of C3H mice are important factors to be considered in designing experiments to study the tumorigenic activity of oestrogens such as DES.     

Influence of age and environment on the induction of mammary tumours by diethylstilboestrol in C3H/HeN-MTV+ mice

C3H/HeN-MTV+ female mice were fed diets containing targeted concentrations of 320 or 640 ppb diethylstilboestrol (DES) starting at 3, 5, 7 or 11 wk of age and continuing throughout their remaining lifespan. Mice were housed in either a single-corridor conventional animal room or in a double-corridor barrier-type animal room. Mice housed in the conventional animal room and started on DES at 7 or 11 week of age developed palpable mammary tumours somewhat sooner than the corresponding groups of mice kept in the barrier animal room. In mice housed in the barrier animal room and exposed to a given DES concentration, there was very little difference between mice started on DES at 3, 5 or 7 wk of age in the exposure time required for the development of palpable mammary tumours. There was a striking difference, however, between mice started on DES at 7 wk and those started at 11 wk of age in the exposure time needed before mammary tumours appeared. Mice started at 11 wk of age developed tumours with, on average, about 4 wk less exposure than did those started at 7 wk. This suggests that treatment between 7 and 11 wk of age had little or no effect on mammary tumour development. In conclusion, both animal-room environment and age at the start of DES treatment influenced the mammary tumour response in female C3H/HeN-MTV+ mice.     

Neoplastic and nonneoplastic responses to chronic feeding of diethylstilbestrol in C3H mice

Over 3000 female C3H/Hen-MTV+ mice continuously received graded dietary levels (0, 2.5, 5, 10, 20, 40, 80, 160, 320, and 640 ppb) of diethylstilbestrol (DES) beginning at weaning. Mice were scheduled to be killed after 3 or 26 wk of exposure and were palpated weekly and removed for histological evaluation when subcutaneous masses reached 1 cm diameter. Mammary tumors were more prevalent than in controls only at 320 and 640 ppb DES. However, palpable mammary tumors appeared significantly earlier than in controls in mice fed 80 ppb and above. Mice killed at 3 wk and later showed a dose-response for several nonneoplastic endpoints. At 3 wk, moderate to severe uterine glandular hyperplasia, lack of corpora lutea, and vaginal keratinization were more prevalent than in controls at 80 ppb; cervical adenosis was more prevalent than in controls at 160 ppb and above. Generally, the prevalence of other nonneoplastic responses such as uterine fibrosis, stromal mucoid changes, and bony trabecular proliferation were increased above control levels only later than 3 wk at 160 ppb and greater. This study demonstrated neoplastic and nonneoplastic responses to DES at and above 80 ppb, but gave no clear evidence of either type of response below this level. Conclusions are, (1) dietary levels of DES causing nonneoplastic effects also cause neoplastic effects when fed chronically, and (2) neoplastic levels of DES may be predicted from a 3 wk feeding study in C3H/HeN-MTV+ female mice based on nonneoplastic responses.     

Interactive responses to diethylstilboestrol in C3H mice

Female C3HeB/FeJ mice were fed diethylstilboestrol (DES) at a dietary concentration of 100 ppb beginning at 6 wk of age. Several oestrogen-sensitive target organs (uterus, vagina, bone and mammary gland) were removed and examined histologically when mice died, became moribund, were killed at scheduled intervals or were removed because of presumptive mammary tumours (palpable mass having a 1-cm diameter). Oestrogen-sensitive histological observations for which there was less than a 100% prevalence and/or severity included uterine fibrosis and glandular hyperplasia, vaginal mucoid stroma and keratinization, mammary adenocarcinomas and osseous trabecular proliferation or marrow fibrosis. Mice from this treated population were grouped according to the specific grade of uterine glandular hyperplasia. Each mouse having a given grade of hyperplasia was matched with a mouse that failed to develop glandular hyperplasia and was fed the 100 ppb DES diet for approximately the same time period. This procedure provided three sets of matched pairs (no hyperplasia v. grade 0; no hyperplasia v. grade 1 and no hyperplasia v. grade 2). Pairwise comparisons were then made in these groups for each of the other oestrogen endpoints. Within each set of matched pairs, mice with glandular hyperplasia had a greater prevalence and/or severity of uterine fibrosis and vaginal mucoid stroma and vaginal keratinization than those without hyperplasia and differences within matched sets were greater as the severity of hyperplasia increased. In contrast, the prevalence of osseous trabecular proliferation or marrow fibrosis were equivalent across all grades of glandular hyperplasia and the prevalence of mammary adenocarcinomas was inversely related to the severity of glandular hyperplasia. These data suggest the existence of a subpopulation of inbred mice that is especially sensitive to DES exposure for uterine and vaginal endpoints and highly insensitive to mammary tumour induction.     

Estrogen-induced thyroid follicular cell adenomas in C57BL/6 mice

Diethylstilbestrol (DES) was fed chronically to C57BL/6 mice at concentrations of 0, 5, 10, 20, 40, 160, 320, or 640 ppb in order to define the dose-response curve for neoplastic responses. The incidence of thyroid follicular cell adenomas was higher in control females than in males and was increased at mid-level doses of DES, especially in males. None were found in mice fed 640 ppb DES, probably because these mice died from other causes before follicular cell adenomas had developed. In both sexes, DES fed at 160 or 320 ppb significantly shortened time-to-onset of these tumors, and 40 ppb increased their probability late in life. It is concluded that DES has a causal relationship to thyroid neoplasia in C57BL/6 mice, and similarities between this and the human disease suggest that C57BL/6 mice may be an appropriate model for human thyroid neoplasia.     

Nonneoplastic changes induced in female C3H mice by chronic exposure to diethylstilbestrol or 17 beta-estradiol

The long-term nonneoplastic effects of estrogenic diets were studied in female C3H/HeJ and C3HeB/FeJ mice. C3H/HeJ mice received diets containing 0, 10, 100, or 500 ppb diethylstilbestrol (DES) or 100, 1000, or 5000 ppb 17 beta-estradiol (E2) from 6 to 110 wk of age. C3HeB/FeJ females were fed diets containing nominal concentrations of 0, 10, 100, or 500 ppb DES from 6 to 136 wk of age. Responses of both strains to DES were qualitatively identical. Histological changes in the reproductive tract induced or increased by DES in both strains and by E2 in C3H/HeJ mice included stromal mucoid changes in the vagina and cervix, epithelial keratinization in the vagina, and glandular hyperplasia in the uterine horns. Increasing doses above 10 ppb DES or 100 ppb E2 increased the prevalence and, in some cases, severity of these responses. Dose-responses to DES for these endpoints were virtually indistinguishable in the two strains. At 10 ppb DES or 100 ppb E2 there were minimal or no observable effects. When the nonneoplastic dose-response data were compared with neoplastic dose-response data previously reported, no consistent relation between doses causing neoplastic and nonneoplastic responses was seen for the two estrogens.     

The effect of age and exposure duration on cancer induction by a known carcinogen in rats,mice, and hamsters

Female Golden Syrian hamsters, F-344 rats, Swiss CD-1 mice, and B6C3F1 hybrid mice were exposed 6 hr/day, 5 days/week to carcinogenic levels of vinyl chloride (VC) for 6, 12, 18, or 24 months (rats and hamsters only). Other groups of rodents were held for 6 or 12 months and then exposed for 6 or 12 months. At the end of the study the incidence of VC-induced neoplasms was compared in each of the groups to assess the effects of duration of exposure and age at the start of exposure on carcinogenicity of VC. In rats, with early initial exposure, hemangiosarcomas, hepatocellular carcinomas, and mammary gland carcinomas occurred with increasing incidence with longer exposure duration. Rats held for 6 months before exposure developed VC-related neoplasms, while rats held 12 months before the start of exposure failed to show a significantly increased incidence of these neoplasms. In hamsters, hemangiosarcomas, mammary gland carcinomas, gastric adenocarcinomas, and skin carcinomas resulted from VC exposure. The highest incidence of malignant neoplasms occurred in hamsters exposed for the first 12 months, whereas exposure begun after 12 months of age did not cause neoplasms. In both strains of mice, VC exposure during the first 6 months of the experiment induced a high incidence of hemangiosarcomas and mammary gland carcinomas. Swiss mice also developed lung carcinomas after only 6 months of exposure. In all three rodent species an initial 12 month exposure to VC was adequate to detect its carcinogenic potential, but the shortened survival of VC exposed mice and hamsters precluded a meaningful comparison with longer periods of exposure. Exposures were most effective when started early in life.     

Normal mammary gland morphology in pubertal female mice following in utero and lactational exposure to genistein at levels comparable to human dietary exposure

The objective of the study was to determine the effect of in utero and lactational exposure to genistein (0, 0.1, 0.5, 2.5 and 10 mg/kg/day) on mammary gland morphology in female B6D2F1 mice at levels comparable to or greater than human exposures. The effect of diethylstilbestrol (DES; 0, 0.1, 1, 10 microg/kg/day) on the mammary gland was also examined as a positive estrogenic control. Pregnant females were treated by daily gavage from gestational day 12 to postnatal day (PND) 20. Female offspring were weaned on PND21 and mammary gland whole mounts were examined for growth (length and area of the epithelial tree), proliferation (number of terminal end buds (TEBs)), and differentiation (density of alveolar buds (ABs)) on PND49. The highest dose of DES induced a significant increase in mammary gland growth (P<0.05) and also decreased the number of TEBs (P<0.06). The density of ABs was not significantly affected by DES. By contrast to DES, genistein had no effect on mammary gland morphology at any dose. These results suggest that in utero and lactational exposure to genistein at levels comparable to or greater than human exposures do not adversely affect mammary gland development in pubertal female B6D2F1 mice.     

Effects of maternal xenoestrogen exposure on development of the reproductive tract and mammary gland in female CD-1 mouse offspring

The objective of this study was to examine the effects of maternal exposure to xenoestrogen, at levels comparable to or greater than human exposure, on development of the reproductive tract and mammary glands in female CD-1 mouse offspring. Effects of genistein (GEN), resveratrol (RES), zearalenone (ZEA), bisphenol A (BPA) and diethylstilbestrol (DES) were examined. Beginning on gestational day 15, pregnant CD-1 mice were administered four daily subcutaneous injections with 0.5 or 10 mg/kg/day of GEN, RES, ZEA or BPA, 0.5 or 10 μg/kg/day of DES dissolved in dimethylsulfoxide (DMSO), or DMSO vehicle (n = 6). Vaginal opening was monitored, 6 animals per group were autopsied at 4, 8, 12 and 16 weeks of age and estrous cyclicity was monitored from 9 to 11 weeks of age. Maternal exposure to xenoestrogen accelerated puberty onset (vaginal opening) and increased the length of the estrous cycle; mice treated with GEN, RES, BPA or DES spent more time in diestrus, and ZEA-treated mice spent more time in estrus. Lack of corpora lutea and vaginal cornification were observed at 4 weeks of age in the high-dose GEN (33%) and RES (17%) groups, and in the high- and low-dose BPA groups (33 and 50%, respectively) and DES groups (83 and 100%, respectively). Lack of corpora lutea and vaginal cornification was observed in the high-dose ZEA group at 4, 8, 12 and 16 weeks of age (83, 100, 83 and 33%, respectively). Mammary gland differentiation was accelerated in ZEA- and BPA-treated mice with corpora lutea at 4 weeks of age. ZEA-treated mice without corpora lutea showed mammary growth arrest at 8, 12 and 16 weeks of age; their mammary glands consisted only of a dilatated duct filled with secreted fluid. Mammary gland growth was similar with xenoestrogens other than ZEA or BPA to that of the controls at all time points. High-dose GEN and RES and high- and low-dose BPA and DES exerted transient effects on the reproductive tract and mammary glands, whereas ZEA exerted prolonged effects.     

Uterine responsiveness to estradiol and DNA methylation are altered by fetal exposure to diethylstilbestrol and methoxychlor in CD-1 mice: effects of low versus high doses

We examined the effects on female CD-1 mice of fetal exposure to low doses of the drug diethylstilbestrol (DES) (0.1 microg/kg/day) and the insecticide methoxychlor (MXC) (10 microg/kg/day) as well as 1000-fold higher doses: 100 microg/kg/day DES and 10,000 microg/kg/day MXC. Pregnant females were administered these chemicals on gestation days 12-18. At 7-8 months of age, female offspring were ovariectomized and implanted for 7 days with a Silastic capsule containing estradiol. Relative to controls, females exposed to the 0.1 microg DES dose showed significantly heavier uteri, while females exposed to the 100 microg DES dose showed significantly lighter uteri. Females exposed prenatally to the 10 microg/kg dose of MXC had significantly heavier uteri relative to females exposed to the 10,000 microg/kg dose of MXC, but neither group differed significantly from controls. Liver weight for females exposed to both doses of DES was significantly greater than controls. Using a microarray approach to analyze DNA methylation, an increase in ribosomal DNA (rDNA) methylation was observed. Sequence data and Southern analysis indicate an increase in 18S rDNA and 45S pre-rDNA methylation in uterine samples exposed prenatally to low and high doses of DES. We thus found opposite effects of fetal exposure to a low and a high dose of DES on the uterine response to estradiol (inverted-U dose-response relationship). In contrast, there was a monotonic dose-response relationship found for prenatal DES exposure on both liver weight and ribosomal DNA hypermethylation.     

Effects of prepubertal exposure to xenoestrogen on development of estrogen target organs in female CD-1 mice

BACKGROUND: There have been no previous reports comparing the effects of prepubertal xenoestrogen exposure on development of the reproductive tract and mammary glands in female mice. The effects of genistein (GEN), resveratrol (RES), zearalenone (ZEA), zeranol (ZER), bisphenol A (BPA) and diethylstilbestrol (DES) were examined. MATERIALS AND METHODS: Beginning at 15 days of age, female CD-1 mice were administered 4 daily subcutaneous injections of 10 mg/kg/day of GEN, RES, ZEA, ZER or BPA, or 10 microg/kg/day of DES dissolved in dimethylsulfoxide (DMSO), or DMSO vehicle. Vaginal opening was checked; estrous cyclicity was monitored from 5, 9 or 21 weeks of age for 21 consecutive days; 6 animals per group were autopsied at 4, 8 and 24 weeks of age. RESULTS: Prepubertal exposure to GEN, ZEA, ZER and DES (but not RES or BPA) accelerated puberty onset (vaginal opening). Vaginal smears indicated that all xenoestrogen-treated mice were cycling, but ZEA-, ZER- and DES-treated mice spent more time in estrus. At 4 weeks of age, absence of corpora lutea (anovulatory ovary) was observed in the untreated controls (33%, 2/6) and the GEN (50%, 3/6), RES (50%, 3/6), ZEA (100%, 6/6), ZER (100%, 6/6), BPA (83%, 5/6) and DES groups (100%, 6/6). At 8 weeks of age, absence of corpora lutea was observed in the ZEA (33%, 2/6) group. Corpora lutea were present in all mice sacrificed at 24 weeks of age. Groups that received prepubertal xenoestrogen injections exhibited no morphological abnormalities of the uterus and vagina, and exhibited mammary gland growth similar to that of the untreated controls at all time-points. CONCLUSION: GEN, ZEA, ZER and DES (but not RES or BPA) caused early vaginal opening; mice exposed to ZEA, ZER or DES spent more time in the estrus phase; ZEA-treated mice had a longer period of anovulatory ovary than other xenoestrogen-treated mice; however, none of the xenoestrogens tested altered the uterine or vaginal morphology or mammary gland growth.     

Mammary tumorigenesis in the rat following prenatal exposure to diethylstilbestrol and postnatal treatment with 7,12-dimethylbenz[a]anthracene.

Pregnant rats were injected with vehicle or 1,2 microgram diethylstilbestrol (DES) during wk 2 or 3 of gestation; their female offspring ( approximately 50 d old) were fed 7,12-dimethylbenz[a]anthrocene (DMBA). The survivors (27 per group) were sacrificed 30 wk later. The three groups did not differ in the number of tumor-bearing animals; however, significantly more palpable mammary tumors arose in both DES-exposed groups than in controls. When DES was given during the second trimester, palpable tumors appeared earlier than in the other two groups. Thus, transplancental exposure to DES potentiated the action of a known carcinogen (DMBA) on rat mammary tissue. These results raise the possibility that, for young women, DES exposure in utero may have affected tissues other than the vagina. Further investigation is warranted, with special emphasis on the effects of DES on mammary and other estrogen-sensitive tissues.     

Reproductive performance among DES exposed daughters compared with that of their mothers

The study was undertaken to determine what the experience of 158 diethylstilbestrol (DES) exposed daughters in the Toledo area has been and whether the rate of pregnancy loss is related to a similar rate in their mothers, indicating a familial factor in the etiology. 45 patients could produce written, documented evidence through their mothers' prenatal records of having been exposed to DES. In these, not only the drug, but also the dose, stage of gestation, and duration were known. In 37 of these (82.2%), definite, benign DES related changes were found in the vagina and cervix. In another 49 patients documented evidence was not available, but all demonstrated the same gross and/or colposcopic changes, thereby giving presumptive evidence of DES exposure. These 94 patients make up Group A. In 64 patients, no documented evidence of DES exposure was obtainable, since their mothers' prenatal records had been lost or destroyed. The mothers themselves recalled using the drug with varying degrees of knowledge about the specifics of dose or duration. None of these daughters had objective findings, by gross or colposcopic examination, suggestive of DES effect. In 20 of them there was some evidence consistent with exposure. These were designated "equivocal findings" and included with the Group B patients. In the group of 94 women who satisfied the criteria of DES exposure by documented history and/or characteristic physical findings (Group A), there were 39 who were sexually active without contraception. The remaining either denied coitus or were regular contraceptive users. 10 patients attempted to conceive for more than 1 year without success, for a primary infertility rate of 25.6%. 29 achieved a total of 46 pregnancies; 22 were delivered at term, and 24 aborted spontaneously, for a pregnancy failure rate of 52.2%. Of the 64 patients with histories of DES exposure but no documented evidence (Group B), there were 24 sexually active without contraceptive use. In these 24 there were 3 who complained of primary infertility, which was defined as regular coitus without contraception for a period of at least 1 year, for a primary infertility rate of 12.5%. The remaining 21 patients had a total of 41 pregnancies. 31 of these resulted in full term live infants. 2 were electively aborted, and 8 were aborted spontaneously. Reproductive histories were available in 105 of the mothers of these daughters. The mothers of the women in both groups had poor reproductive histories. The reproductive performance of Group B daughters was better than that of their mothers and closely approximated that usually quoted for the general population. The performance of group A mothers was significantly worse than that of their mothers, in whom the pregnancy failure rate already was high. The data indicate that the DES exposed daughters have a higher reproductive failure rate than their mothers, while that of DES unexposed daughters is lower. The existence of a familial factor is not supported.     

Timing and recovery of postweaning exposure to diethylstilbestrol on early pregnancy in CD-1 mice

Exposure timing could play an important role in the effects of estrogenic endocrine disrupting chemicals (EEDCs) on early pregnancy. This study examined the sensitivity of different exposure periods from weaning to gestation day 4.5 (D4.5) to 50 ppb diethylstilbestrol (DES, a test EEDC) diet on embryo implantation and potential recovery upon temporary cessation of DES exposure in CD-1 mice. Peripubertal (3–5 weeks old) DES exposure reduced the numbers of corpora lutea and implantation sites. Postpubertal (5–7 weeks old) DES exposure did not have significant effects on early pregnancy. Postmating (D0.5–D4.5) DES exposure affected postovulation events leading to impaired embryo implantation. A 5-day premating rest from 5-week DES exposure (3–8 weeks old) resulted in recovery of early pregnancy rate. These data demonstrate that peripubertal and postmating periods are sensitive windows to endocrine disruption of early pregnancy and temporary cessation of exposure could partially alleviate adverse effects of DES on early pregnancy.     

Chronic inhalation toxicity and carcinogenicity study of propylene oxide in Wistar rats

Four groups of 100 Wistar rats of each sex were exposed by inhalation to 0, 30, 100 or 300 ppm propylene oxide for 6 hr/day, 5 days/wk for 28 months. After 12, 18 and 24 months ten rats/sex/group were killed to provide interim haematological, biochemical and urinary data. Mortality was increased by wk 115 in both sexes in the 300-ppm group and by wk 119 in females of the 100-ppm group. Body weights were lower than those of the controls throughout the study in males of the 300-ppm group and in females of the 300-ppm group during the first year of the study. Increased incidences of degenerative and hyperplastic changes of the nasal mucosa were observed in all exposed groups. Exposure to 300 ppm propylene oxide was associated with an increased incidence of both benign and malignant mammary tumours in females. There was no increase in the incidence of any particular type of tumour other than mammary tumours. The total number of rats bearing malignant tumours at sites other than the mammary glands was increased in both sexes in the 300-ppm group compared with the controls.     

Lack of effect of dietary diethylstilbestrol on reproductive performance.

Groups of male or female mice were pretreated for 2 wk and 1 wk, respectively, with flesh (liver or muscle) diets prepared from steers. In one experiment diethylstilbestrol (DES) was added to the diet at 0.5 or 5.0 ppb. In a second experiment diets prepared from DES-implanted steer flesh (liver or muscle) were fed. Tissues used in the control diet and DES-added diets were from DES-free steers. The animals were allowed to mate and diets continued until the first litter was delivered. Increasing DES levels in either liver or muscle diets or flesh from DES-implanted steers resulted in no significant differences either in litter size or in the number of fertile male or female mice between the control group and experimental groups. The offspring from each litter were mated and showed no significant difference in their reproductive performance. No abnormalities were noted in any offspring.     

An evaluation of changes and recovery in the olfactory epithelium in mice after inhalation exposure to methylethylketoxime

Methylethylketoxime, also known as MEKO or 2-butanone oxime (CAS No. 96-29-7), is a clear, colorless to light yellow liquid at room temperature. It is an industrial antioxidant used as an antiskinning agent in alkyd paint, an industrial blocking agent for urethane polymers, and a corrosion inhibitor in industrial boilers, and can be found in some adhesives and silicone caulking products. Male CD-1 mice were exposed 6 h/day, 5 days/wk, for 1, 2, 4, or 13 wk via whole-body inhalation exposures to MEKO vapor concentrations of 0, 3 +/- 0.1, 10 +/- 0.3, 30 +/- 1, or 100 +/- 2 ppm (10 mice/group/interval). Satellite animals were removed after 1, 2, 4, or 13 wk of exposure and allowed to recover for 4 or 13 wk (5 mice/group/interval). After termination, the nasal turbinates were evaluated microscopically, and cross-sectional nasal maps of the lesions were prepared. At the end of the 1-, 2-, 4-, and 13-wk exposure periods, degeneration of the olfactory epithelium lining the dorsal meatus was seen in the anterior region of the nasal cavity. In a few instances, the olfactory epithelium covering the tips of the nasoturbinal scrolls projecting into the dorsal region of the nasal cavity was also degenerated. Large areas of olfactory epithelium lying laterally and posteriorly were unaffected. In general, approximately 10% or less of the total olfactory tissue was affected. In several instances, the degenerated olfactory epithelium was reepithelialized by squamous/squamoid and/or respiratory types of epithelium. Degeneration, which was dose related in incidence and severity, was seen in mice exposed to 30 and 100 ppm after 1 wk of exposure and in several mice exposed to 10 ppm after 13 wk of exposure. The incidence and severity of the degeneration present after 1 wk of exposure did not increase with the longer exposures. The olfactory degeneration was reversible. Recovery was complete within 4 wk following exposures at 10 ppm and nearly complete within 13 wk after exposures at 30 and 100 ppm. A no-observed-effect level (NOEL) for the olfactory degeneration was considered to be 3 ppm.     

Ovalbumin-induced airway inflammation and fibrosis in mice also exposed to ultrafine particles

A murine model of allergen-induced airway inflammation was used to examine the effects of exposure to ultrafine particles (PM(2.5)) on airway inflammation and remodeling. Lung inflammation was measured by quantitative differential evaluation of lung lavage cells. Alterations in lung structure (airway remodeling and fibrosis) were evaluated by quantitative biochemical analysis of microdissected airways and by histological evaluation of stained lung sections. The same total number of cells was observed in lavage fluid from animals exposed for 4 wk to ovalbumin alone or to ovalbumin for 4 wk immediately before or after 6 exposures over a period of 2 wk to 235 ug/m(3) of PM(2.5). Mice exposed to ovalbumin for 6 wk with concurrent exposure to PM(2.5) during wk 5-6 had a significant decrease in the total number of cells recovered by lavage as compared with the group exposed to ovalbumin alone. There were no significant differences in the cell differential counts in the lavage fluid from mice exposed to ovalbumin alone as compared with values from mice exposed to ovalbumin and PM(2.5) under the protocols studied. Airway structural changes (remodeling) were examined by three different quantitative methods. None of the groups exposed to ovalbumin and PM had a significant increase in airway collagen content evaluated biochemically (i.e., total airway collagen) as compared to the matched groups of mice exposed to ovalbumin alone. Airway collagen content evaluated histologically by sirius red staining showed significant increases in all of the animals exposed to ovalbumin, with or without PM, and no apparent difference between the ovalbumin group and mice exposed to PM with ovalbumin. The findings were consistent with an additive, or less than additive, response of mice to exposure to PM and ovalbumin. Air or PM exposure alone for 2 wk did not result in observable goblet cells in the airways, while mice exposed to ovalbumin aerosol alone for 4 wk had about 20-25% goblet cells in their conducting airways. Sequential exposure to ovalbumin and PM (or vice versa) caused significant increases in goblet cells (to about 35% of total cells) in the conducting airways of the exposed mice. We conclude that when mice with allergen-induced airway inflammation induced by ovalbumin are also exposed to PM(2.5), the lung inflammatory response and airway remodeling may be modified, but that this altered response is dependent upon the sequence of exposure and the duration of exposure to ovalbumin aerosol. At the concentrations of PM tested, we did not see changes in airway fibrosis or airway reactivity for animals exposed to ovalbumin and PM(2.5) as compared with animals exposed only to ovalbumin aerosol. However, goblet-cell hyperplasia was significantly increased in mice exposed concurrently to ovalbumin and PM(2.5) as compared with mice exposed to ovalbumin alone.     

己烯雌酚单独或与乌拉坦共同暴露对新生和5周龄小鼠的致肿瘤作用

目的研究不同生长阶段ICR小鼠对己烯雌酚(DES)暴露的敏感性及DES暴露频率与肿瘤发生的关系,探索乌垃坦(Ure)对DES的肿瘤促进作用。方法新生及5周龄小鼠分对照、溶剂、DES、Ure及Ure+DES联合应用组。新生鼠在d 14,5周龄鼠在出生第5周末,均以500 m.gkg-1Ure ip;新生鼠分别在d 1,8和15 ip DES共3次;5周龄鼠从出生第6周起ip DES,每周1次,连续18次。至26周时剖检,观察肿瘤发生情况。结果新生鼠和5周龄鼠均有明显的肺肿瘤发生。新生鼠DES(2.0,4.0和8.0 m.gL-1)给药组,肺肿瘤发生率分别为16.7%,22.4%和43.1%;Ure+DES(2.0,4.0和8.0 m.gL-1)为70.4%,90.9%和70.8%。5周龄鼠DES 5,15及50 mg.kg-1时,肺肿瘤发生率分别为52.5%,32.1%和23.0%;Ure+DES(5,15和50 m.gL-1)为54.1%,58.5%和62.0%。结论外源DES对同一品系小鼠不同生长阶段的致肿瘤作用不同,新生鼠比成年鼠对DES和Ure联合作用有更高的肿瘤易感性,Ure对DES有一定的肿瘤促进作用。     

Ovalbumin-induced airway inflammation and fibrosis in mice also exposed to ozone

A murine model of allergen-induced airway inflammation was used to examine the effects of exposure to ozone on airway inflammation and remodeling. Sensitized BALB/c mice were exposed to ovalbumin aerosol for 4 wk before and after 2 wk of exposure to either 0.2 ppm or 0.5 ppm ozone. Other groups of mice were exposed to ovalbumin aerosol for 6 wk with continuous concurrent exposure to ozone during wk 1-6, or during intermittent concurrent exposure to ozone. Lung inflammation was measured by quantitative differential evaluation of lung lavage cells and by histological evaluation of stained lung sections. Alterations in lung structure (airway fibrosis) were evaluated by quantitative biochemical analysis of microdissected airways. The same total number of cells was observed in lavage fluid from animals exposed for 4 wk to ovalbumin alone or to ovalbumin for 4 wk immediately before or after exposure to 2 wk of 0.2 or 0.5 ppm ozone. Mice exposed to ovalbumin for 6 wk with concurrent exposure to either 0.2 ppm or 0.5 ppm ozone during wk 3-6 had a significant decrease in the total number of cells recovered by lavage. Values as low as 7% of the cell number found in mice exposed to ovalbumin aerosol alone were observed in the mice exposed to ovalbumin plus 0.2 ppm ozone during wk 3-6. There were significant differences in the cell differential counts in the lavage fluid from mice exposed to ovalbumin alone as compared with values from mice exposed to ovalbumin and ozone under all of the protocols studied. When ozone was given for 2 wk prior to ovalbumin exposure (Experiment 1), there were a high percentage of macrophages and low percentages of lymphocytes and eosinophils in the lung lavage. When ozone was given for 2 wk after ovalbumin exposure (Experiment 2), there were a moderate percentage of macrophages, a low percentage of eosinophils, and a high percentage of lymphocytes in the lung lavage. When ozone and ovalbumin were given simultaneously (Experiments 3 and 4), there were a high percentage of macrophages in the lavage with 0.2 ppm ozone and a high percentage of eosinophils. Ozone appears to antagonize the specific inflammatory effects of ovalbumin exposure, especially when given before or during exposure to ovalbumin. Airway remodeling was examined by two different quantitative methods. None of the groups exposed concurrently to ovalbumin and ozone had a significant increase in airway collagen content as compared to the matched groups of mice exposed to ovalbumin alone. The findings were consistent with an additive response of mice to simultaneous exposure to ovalbumin and ozone. Ozone exposure alone for 6 wk did not affect the number of goblet cells in the airways, while mice exposed to ovalbumin aerosol alone for 6 wk had about 25% goblet cells in their conducting airways. Concurrent exposure to ovalbumin and 0.2 ppm ozone caused significant increases in goblet cells (to 43% of total cells) in the conducting airways of the exposed mice. We conclude that when mice with allergen-induced airway inflammation induced by ovalbumin are also exposed to ozone, the lung inflammatory response may be modified, but that this altered response is dependent on the sequence of exposure and the concentration of ozone to which they are exposed. At the concentrations of ozone tested, we did not see changes in airway fibrosis. However, goblet-cell hyperplasia appeared to be increased in mice exposed concurrently to ovalbumin and 0.2 ppm ozone.