Increased frequencies of aberrant sperm as indicators of mutagenic damage in mice

Seminal Cytology and Reproductive Toxicology of N-Chloropiperidine

Induction of sperm abnormality in mice and hamster and reproductive toxicity in mice was examined following chronic exposures (ad libitum) to N-chloropiperidine (NCP). The results showed that significant levels of abnormal sperm in the NCP treated group were observed after five weeks of exposure. The time of the appearance of NCP-induced anomalous sperm suggested that the compound did not affect late spermatocytes and spermiogenesis. Reproductive toxicological analysis based on moles, implantations, and offspring per pregnancy revealed that while the toxic effect of ethylmethane sulfonate was evident within the first week of treatment, NCP-induced toxicity was observed only after five weeks of treatment. The data further showed that in matings where both parents were exposed to NCP, the frequencies of moles, implantations, and offspring per pregnancy were fewer than those observed in single parent exposure.

An in vivo evaluation of induction of abnormal sperm morphology by ivermectin MSD (Mectizan)

The in vivo effects of orally administered ivermectin (Mectizan) on sperm head morphology of albino mice were evaluated. Four different dose levels of 0.25, 0.5, 1.0 and 1.5 x the human therapeutic dose of 150 g kg(-1) body weight, were administered to the animals. The animals were exposed to a single oral treatment. The sperm of the mice from the cauda epididymes were examined 5 and 7 weeks after treatment. Ivermectin (Mectizan) induced sperm head abnormalities; however, the induction was not significantly elevated above the negative control value. Furthermore, the induction of the sperm head abnormalities was not strictly dose-dependent and there was also no correlation between dose level of administered drug and incidence of abnormal sperms. This indicates that the drug might not be mutagenic.

Role of vitamin C on lead acetate induced spermatogenesis in swiss mice

In the present study significantly increased lipid peroxidation value (LPP) after a single intraperitioneal injection of lead acetate (LA) (100 mg/kg b.w.) indicated enormous generation of Reactive Oxygen Species (ROS). Lead-induced ROS has a direct inhibitory effect on the growth and differentiation of the spermatogonial cells showing a significant decline in sperm count. Chromosomal analysis of the primary spermatocytes at week 4 post-treatment in lead-treated mice revealed significantly higher no of aberrant cells including chromosomal deficiency, autosomal and XY-asynapsis plates compared to untreated control mice, Sperm morphology studies at week 1-4 and at week 8 post-treatment, indicated higher percentage of deformed sperm population compared to vehicle injected groups of mice. Supplementation of vitamin C (Vit C) at a dose of 10 mg/kg body weight to lead-treated mice groups, however, significantly reduced the LPP with a concomitant increase in sperm count, marked decrease in the no of aberrant cells and significant decline in the percentage of morphologically abnormal sperm population. Protective role of Vit C in combating lead-induced oxidative stress in mice testicular cells, has been discussed.

An in vivo evaluation of induction of abnormal sperm morphology by some anthelmintic drugs in mice

Using the murine sperm-head abnormality test, the mutagenicity of pyrantel pamoate, levamisole, albendazole, mebendazole and niridazole was evaluated. Pyrantel pamoate and niridazole induced increases in sperm-head abnormalities statistically significant over the negative controls at all the dose levels that were considered; the induction was dose-dependent indicating that both drugs might be mutagenic. Levamisole, albendazole, mebendazole and thiabendazole, all were unable to induce statistically significant increases in sperm-head abnormalities over the negative controls at all the dose levels tested; there was no correlation between dose level of administered drugs and incidence of abnormal sperms, indicating that the drugs might not be mutagenic.

Review of reproductive and developmental toxicity of 1,3-butadiene

Toxic doses of 1,3-butadiene (BD) have been reported to cause reproductive and/or developmental toxicity. Regardless of the strain used, mice were always affected by BD at lower doses than rats, an expected observation, based on well recognized differences in pharmacokinetic (PK) parameters in these two species. Because the mouse is particularly sensitive to BD in comparison with other laboratory species, and there are important functional and anatomical differences between humans and mice, the NOELs and LOELs identified for BD for various reproductive endpoints in mice may not be relevant to human reproductive risk. In mice, the LOELs for reproductive endpoints include developmental toxicity at 200 ppm, genotoxic effects at 500 ppm (mouse spot test), ovarian atrophy in females at 6.25 ppm (carcinogenicity study), reduced testicular weights at 200 ppm and testicular atrophy at 625 ppm BD in males (carcinogenicity studies), low incidences of abnormal sperm heads at 1000 and 5000 ppm BD (sperm head morphology study), small reversible increases in resorption at 1250/1300 ppm or 5000 ppm (dominant lethal studies), and other possible sequelae of genotoxicity resulting from exposure of male mice at 12.5 ppm BD and higher (dominant lethal study). When available, the much higher NOELs and LOELs of other species tested for the same endpoints should be considered. For example, maternal and developmental NOELs for BD in the rat were 200 and 1000 ppm, respectively, and 40 ppm in the mouse. Likewise, exposure of cohabited pairs of rats, guinea pigs and rabbits or of female dogs to BD concentrations as high as 6700 ppm for 8 months did not impair fertility or cause testicular or ovarian atrophy in these species. Thus, consideration of these remarkable species-dependent differences in toxicity is necessary. In addition, there are alternative scientific interpretations for some of the mouse studies and this review attempts to address these areas. For example, it may be incorrect to categorize results indicating weak in vivo genotoxic effects in male mice (sperm head morphology and dominant lethal studies) at 12.5 ppm BD and higher as reproductive effects because concentrations of BD as high as 5000 ppm did not affect mating, fertility or live litter sizes, even in this sensitive species. Similarly, it may be inappropriate to identify the ovary as a target organ for reproductive risk since the ovarian atrophy in mice was identified after completion of the normal reproductive life and after more than 15 months of exposure. Neither ovarian nor testicular atrophy occurred in Sprague-Dawley rats after exposure to BD concentrations as high as 8000 ppm for 105 (females) or 111 (males) weeks.

Toxicological effects of ziram, thiram, and dithane M-45 assessed by sperm shape abnormalities in mice

The three commonly used dithiocarbamate fungicides ziram, thiram, and dithane M-45 were investigated for their mutagenic and carcinogenic potency using sperm shape abnormalities in mice. The fungicides were administered intraperitoneally in single and cumulative doses. All three of the fungicides tested were found to induce significant increase in the frequency of abnormal sperm at all the doses, and a linear dose effect was observed.

Chromosome aberrations in spermatogonia and sperm abnormalities in Curacron-treated mice

Curacron is an organophosphorus pesticide widely used in cotton fields. In order to assay its mutagenic potential in mammalian germ cells chromosomal aberrations in spermatogonial cells and sperm abnormalities were examined in mice after Curacron treatment. For studying chromosomal aberrations mice were treated both acutely (single treatment) and subacutely (for 5 consecutive days) with 3 dose levels of Curacron, 12, 36 and 72 mg/kg. Curacron was found to produce a significant increase in structural chromosomal aberrations after acute and subacute treatments. This increase was dose-dependent. A dose-dependent inhibition in mitotic activity in spermatogonia was also found. For studying sperm abnormalities mice were treated for 5 consecutive days with 20, 40 and 60 mg/kg. Morphological sperm abnormalities increased significantly after treatment with Curacron. The increase was dose-dependent. An inhibition of 40.2% in sperm count and of 74.5% in sperm motility occurred after treatment with 60 mg/kg Curacron. These results show that Curacron has a damaging effect on spermatogonial cells as well as on sperm morphology.

Relative genotoxicity of trichloroacetic acid (TCA) as revealed by different cytogenetic assays: bone marrow chromosome aberration, micronucleus and sperm-head abnormality in the mouse

Trichloroacetic acid (TCA) has been tested for mutagenicity in a mouse in vivo system. Three different cytogenetic assays--bone marrow chromosomal aberrations, micronucleus and sperm-head abnormalities--have been carried out. Swiss mice have been treated with the chemical, administered via different routes (i.p. and p.o.), and in three acute and/or fractionated doses (5 consecutive daily) equivalent to the highest acute dose, and their cells sampled at different intervals. A variety of anomalies, occurring in higher percentages compared to controls, was observed in all cases. Comparison between single and fractionated dosing revealed the single dosing to be more effective cytogenetically. The results were route and time-dependent but not dose-responsive (exclusive of gaps). The relative sensitivity of the assays has been found to be: chromosome aberration greater than sperm-head abnormality greater than micronucleus. The results revealed the genotoxic property of TCA in the present test system.

Reproductive tract lesions resulting from subchronic administration (63 days) of tri-o-cresyl phosphate in male rats

An initial dose-range pilot study where animals were gavaged with between 100 and 1600 mg tri-o-cresyl phosphate (TOCP)/kg/day for 14 days resulted in decreased epididymal sperm density and disruption of the seminiferous epithelium in 100% of treated animals. A subchronic 63-day study (reflecting the 49-day length of the rat seminiferous epithelium cycle plus the 14-day transit time of spermatids through the epididymis was initiated. Dose-dependent (10 to 100 mg TOCP/kg/day) decreases in cauda epididymal sperm motility and density, testicular enzyme activities, and alterations in sperm morphology were observed. Concurrent pair-fed controls (matched to the highest dose group, 100 mg TOCP/kg/day) indicated that weight loss resulting from TOCP administration had minimal contributory effects to the testicular toxicity seen. Plasma alpha-tocopherol acetate (vitamin E) and testosterone concentrations were unaffected. Tri-p-cresyl phosphate (TPCP), the nonneurotoxic structural analog of TOCP, produced no toxic effects, demonstrating the necessity of the ortho-cresol moiety for induction of damage. A minimum effective (threshold) dose for observable testicular toxicity was determined to be 10-25 mg TOCP/kg in this study. These data suggest that TOCP interferes with spermatogenic processes and sperm motility directly and not via an androgenic mechanism or decreased vitamin E availability.

Effect of ethylene glycol monomethyl ether on spermatogenesis, dominant lethality, and F1 abnormalities in the rat and the mouse after treatment of F0 males

Adult male CD rats and CD-1 mice were given a single oral dose of ethylene glycol monomethyl ether (EGM) at 0, 500, 750, 1,000, or 1500 mg/kg. Groups of 10 were killed at weekly intervals after dosing for analysis of sperm counts and morphology or testicular histology; further groups of 10 were sequentially mated to pairs of virgin females to test for dominant lethality or gross foetal malformations in the F1 generation (F1 abnormalities). EGM was found to deplete the spermatocytes of both species severely, principally pachytene cells, but with other stages affected with increasing dose. A delay in the progression of spermatogenesis may account for a discrepancy between the apparent stage-specificity of damage deduced from lowered sperm counts and that observed histologically. In the rat, morphological abnormalities were observed in sperm that had been exposed as spermatocytes; in the mouse, however, the sensitive cells were the late spermatocytes and early spermatids. In all these parameters there was an indication of a dose-response relationship in both rats and mice. In the mating studies EGM induced a dose-related decrease in fertility 5 weeks after dosing in the rat, but complete sterility in all but the lowest dose after 6 weeks. In contrast, EGM had no effect on the reproductive capacity of the mouse. There was no statistically significant evidence for the induction of dominant lethal mutations or F1 abnormalities in either species. A single oral dose of cyclophosphamide (CTX) at 100 mg/kg induced a significant increase in dominant lethality in both species. CTX reduced the number of total implants in the rat and induced a nonsignificant increase in the number of abnormal offspring sired by treated male mice.

Evaluation of chemicals used for drinking water disinfection for production of chromosomal damage and sperm-head abnormalities in mice

Chemical oxidants are commonly added during water treatment for disinfection purposes. These chemicals have not been tested previously for their ability to induce genetic damage in vivo. Chlorine (hypochlorite and hypochlorous acid), monochloramine, chlorine dioxide, sodium chlorite, and sodium chlorate were evaluated for induction of chromosomal aberrations and micronuclei in bone marrow of CD-1 mice, and for induction of sperm-head abnormalities in B6C3F1 mice. Oral administration of chlorine at pH 8.5 (where hypochlorite predominates) at dose levels equivalent to approximately 4 and 8 mg/kg/day induced significant increases in the level of sperm-head abnormalities. There was no evidence of other effects with any of the disinfectants. Halogenated acetonitriles, which have previously been shown to form in the stomach following oral dosing of sodium hypochlorite to rats, were also tested in the sperm-head abnormality assay but gave no indication of an effect.

Strain differences in the concentration, motility and morphology of epididymal sperm in relation to puberty in mice

Changes in the concentration, motility and morphology, of epididymal sperm have been evaluated in males of between 40 and 100 days of age in BALB, CBA, C3H and C57BL strains of mice. Particular attention was paid to sperm morphology, and a multiple entry classification system was used for its quantitation. At 40 days in each of the 4 strains studied sperm were few in numbers with poor motility and highly atypical morphology, particularly in the head region. From 80 days of age values for the 3 parameters were within the normal range. At equivalent ages during puberty the 4 strains differed in the concentration and motility of epididymal sperm, indicating difference in the time of onset of puberty between the strains. However, once adulthood was reached the strains differed only in the percentage of normal forms and in the frequency distribution of sperm with the various morphological abnormalities.

An evaluation of the mouse sperm morphology test and other sperm tests in nonhuman mammals. A report of the U.S. Environmental Protection Agency Gene-Tox Program

The literature on the mouse sperm morphology test and on other sperm tests in nonhuman mammals was reviewed (a) to evaluate the relationship of these tests to chemically induced spermatogenic dysfunction, germ-cell mutagenicity, and carcinogenicity, and (b) to make an interspecies comparison to chemicals. A total of 71 papers were reviewed. The mouse sperm morphology test was used to assess the effects of 154 of the 182 chemical agents covered. 4 other murine sperm tests were also used: the induction of acrosomal abnormalities (4 agents), reduction in sperm counts, (6 agents), motility (5 agents), and F1 sperm morphology (7 agents)). In addition, sperm tests for the spermatogenic effects of 35 agents were done in 9 nonmurine mammalian species; these included analyses for sperm count, motility, and morphology, using a large variety of study designs. For the mouse sperm morphology test, 41 agents were judged by the reviewing committee to be positive inducers of sperm-head shape abnormalities, 103 were negative, and 10 were inconclusive. To evaluate the relationship between changes in sperm morphology and germ cell mutagenicity, the effects of 41 agents on mouse sperm shape were compared to available data from 3 different mammalian germ-cell mutational tests (specific locus, heritable translocation, and dominant lethal). The mouse sperm morphology test was found to be highly sensitive to germ-cell mutagens; 100% of the known mutagens were correctly identified as positives in the sperm morphology test. Data are insufficient at present to access the rate of false positives. Although it is biologically unclear why one might expect changes in sperm morphology to be related to carcinogenesis, we found that (a) a positive response in the mouse sperm morphology test is highly specific for carcinogenic potential (100% for the agents surveyed), and (b) overall, only 50% of carcinogens were positive in the test (i.e., sensitivity approximately equal to 50%). Since many carcinogens do not produce abnormally shaped sperm even at lethal doses, negative findings with the sperm test cannot be used to classify agents as noncarcinogens. We conclude that the mouse sperm morphology test has potential use for identifying chemicals that induce spermatogenic dysfunction and perhaps heritable mutations. Insufficient numbers of chemicals agents have been studied by the other sperm tests to permit similar comparisons. A comparison of 25 chemicals tested with sperm counts, motility, and morphology in at least 2 species (including man, mouse and 9 other mammals) demonstrated good agreement in response among species. With further study, interspecies comparisons of chemically induced sperm changes may be useful for predicting and evaluating human effects.

Gossypol--an effective male contraceptive was not mutagenic in sperm head abnormality assay in mice

Gossypol acetic acid, a potential male anti-fertility compound, was investigated for its mutagenic effects in the mouse sperm head abnormality assay. Compared with the controls, the chemical at 20 and 40 mg/kg doses did not increase detectable sperm head abnormalities in mice.

Comparative study of the genotoxic properties of Eastern and Western U.S. shale oils, crude petroleum, and coal-derived oil

A multiple bioassay approach was used to characterize and compare the genotoxicities of an Eastern U.S. (Kentucky) shale oil with the genotoxicities of Western U.S. shale oil, petroleum crude oil, and a coal-derived fuel oil. While the coal-derived oil was mutagenic in the Salmonella/microsome mutagenicity (Ames) assay, the shale oils had negligible to weak mutagenicity, and petroleum crude oil was not mutagenic. All the samples were also tested in the following mammalian test systems: an in vitro sister-chromatid exchange (SCE) assay in human lymphocytes and in vivo tests for induction of sperm abnormalities, micronuclei, and SCE in bone marrow of mice. Slight but statistically significant increases (P less than 0.001) in SCE in human lymphocytes were induced by all samples except petroleum crude oil. Neither sample induced a significant number of mutational events in either of the in vivo systems. In these preliminary studies no major differences in the genotoxicities of Eastern and Western shale oils were observed. The results were consistent with the following order of mutagenic potency: coal oil greater than Eastern and Western shale oil greater than petroleum crude oil.

Mithramycin- and triethylene melamine- induced sperm abnormalities in Lakeview hamsters

The sperm abnormality-inducing action of two potential mutagenic agents mithramycin and triethylene melamine (TEM), in inbred Lakeview hamsters was studied and results compared with similar investigations in mouse. Test hamsters received subacute intraperitoneal exposures ranging from 0.01 to 0.25 mg/kg body weight with either agent for 5 consecutive days. Testis weights, epididymal sperm numbers, and body weights were also monitored at weeks 1, 4, and 10 after treatment. Mithramycin-treated hamsters showed 21 times more sperm abnormalities than control (25% vs. 1.2%) whereas TEM elevated sperm abnormalities by eight fold. The frequency and type of aberrant sperm varied with dose and time, being the highest at weeks 1 or 4, rather than week 10, with either agent. Sperm number and testis weights remained depressed considerably from 4 to 10 weeks after treatment with either agent. Body weights in chemically treated hamsters remained within 28% of control for the test period. Even though our findings were in general agreement with those reported for mouse, the magnitude of the response and the stage of spermatogenic sensitivity in the chemical induction of sperm abnormalities in the two species were different.

Male fertility, sister chromatid exchange, and germ cell toxicity following exposure to mixtures of chlorinated phenoxy acids containing 2,3,7,8-tetrachlorodibenzo-p-dioxin

Fertility and sperm number, motility, and morphology were analyzed in male C57BL/6 mice exposed to various mixtures of 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlor-ophenoxyacetic acid (2,4,5-T), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the diet for 8 wk. Somatic cell (bone marrow) sister chromatid exchange frequencies were also evaluated in mice injected with similar chemical mixtures. The concentration of the test chemicals was such that the average daily feeding dose in the three mixtures or control was 40 mg/kg 2, 4-D, 40 mg/kg 2,4,5-T, and 2.4 micrograms/kg TCDD; 40 mg/kg 2,4-D, 40 mg/kg 2,4,5-T and 0.16 microgram/kg TCDD; 20 mg/kg 2, 4-D, 20 mg/kg 2,4,5-T, and 1.2 micrograms/kg TCDD; or no chemical added (control). No significant dose-related effects were observed in the treated mice compared to the control group.

Antispermatogenic effects of ethyl methanesulfonate and benzo[a]pyrene in PD4 Lakeview hamsters

Mammalian sperm seems to provide an excellent cell type for monitoring mutagenic and other toxicological damage to the germinal tissue. Studies with mice indicated that most agents known for their mutagenic activity in vivo produced marked elevations in sperm abnormalities. To determine whether this response is typical of other species, groups of inbred Lakeview hamsters were exposed to ethyl methane-sulfonate (EMS) and benzo[a]pyrene (BP) in five daily subacute ip doses ranging from 5 to 125 mg/kg and 2 to 50 mg/kg, respectively. Percentage of abnormal sperm, testis weight, and body weight were monitored at wk 1, 4, and 10 after treatment. EMS exposures increased the frequency of sperm abnormalities and reduced sperm numbers and testis weights. Body weights were also affected. BP exposures did not induce sperm abnormalities; however, there were marked reductions in sperm number and testis weight. These findings are in agreement with results of EMS studies in the mouse; however, BP exposure did induce sperm abnormalities in the mouse.

Effects of thio-tepa and hydroxyurea on sperm production in Lakeview hamsters

The spermatogenic cell sensitivity in the induction of sperm abnormalities by two antineoplastic agents, thio-TEPA and hydroxyurea in inbred Lakeview hamsters was studied and the results were compared with those of similar investigations with mice. Testis weights, epididymal sperm numbers, and body weights were also monitored up to 12 wk after treatment. Thio-TEPA administration increased sperm abnormalities and reduced testis weights as well as sperm numbers in a dose-dependent manner at wk 4 and 12 after treatment. Hydroxyurea administration was ineffective in inducing sperm abnormalities, but testis weights and sperm numbers were adversely affected dose-dependent changes in body weights after treatment with either agent were also recorded. The findings with thio-TEPA on sperm morphology agree with those reported for the mouse. However, unlike the results of the mouse studies, hydroxy-urea effects on sperm shape were not observed in the hamster.

The effect of hydroxyurea and mitomycin C on sperm motility in mice

The mutagen, mitomycin C, and the teratogen, hydroxyurea, were found to decrease sperm motility in mice in a dose-dependent manner. Positive results with these compounds suggest that sperm motility may have been decreased through either mutations or developmental disturbances. Sperm motility can be determined quickly and may be done in conjunction with a sperm-morphology assay.

Lack of an indication of mutagenic effects of dinitrotoluenes and diaminotoluenes in mice

The mutagenic effects of 2,4-dinitrotoluene (2,4-DNT), purified and technical grades, 3,5-DNT, 2,4-diaminotoluene (2,4-DAT), and 2,5-DAT were tested in mice using one or more of the following: the dominant lethal assay, the sperm morphology test and/or the recessive spot test. Compounds were administered by both intraperitoneal (IP) injection and gavage, and comparisons were made between controls and treated groups as well as between routes of administration. None of the five compounds tested produced a significant response in any of the systems employed. Treatment with purified 2,4-DNT and 3,5-DNT resulted in marked reductions in the percent of fertile matings. These data indicate a lack of mutagenicity of these compounds in the test systems employed here. The observed fertility effects are consistent with previously published data on DNT-induced testicular damage.

Increases in morphologically abnormal sperm in rats exposed to Co60 irradiation

We have investigated the effects of testicular exposure to different doses of Co60 radiation on sperm morphology in F-344 rats. The results indicate that from 150 rad to 500 rad gamma irradiation causes statistically significant, dose-related increased in 1) the percent of morphologically aberrant sperm and 2) the frequency of tailless sperm. Both of these effects were detectable in sperm which were derived from treated spermatid, spermatocytes, and spermatogonial cells. These data indicate that the development of a sperm morphology assay in rats is feasible.