Developmental Toxicity of Bromoxynil in Mice and Rats

Developmental Toxicity of Bromoxynil in Mice and Rats. ROGERS,J. M., FRANCIS, B. M., BARBEE B. D., AND CHERNOFF, N. (1991).Fundam. Appl. Toxicol 17, 442–447. The developmental toxicityof the wide-spectrum herbicide bromoxynil (bromoxynil phenol;3,5-dibromo-4-hydroxyphenyl cyanide) was evaluated in Sprague-Dawleyrats and Swiss-Webster mice, and the developmental toxicityof its octanoate ester (2,6-dibromo-4-cyanophenyl octanoate)was evaluated in Sprague-Dawley rats. Animals were treated fromDay 6 to Day 15 of gestation [presence of sperm or semen plug= 0 of gestation]. The doses administered were as follows: bromoxynilphenol in the mouse, 342, 114, and 38 µmol/kg/day; bromoxynilphenol and bromoxynil octanoate in the rat, 54, 18, and 6 µmol/kg/day.Some animals were killed on selected days during treatment formeasurement of organ weights sensitive to stress. In mice treatedwith bromoxynil phenol, maternal mortality was noted at 114and 342 µmol/kg/day, but surviving females gained weightnormally. Liver to body weight ratios increased with increasingdose, but no consistent effect was seen on adrenal, thymus,or spleen weights. Fetuses of mice treated with the highestdose of bromoxynil phenol were of lower weight and had a higherincidence of supernumerary ribs than controls. In rats, bromoxynilphenol and its octanoate ester at the highest doses used causedno mortality but resulted in only transient decreases in maternalweight gain and significantly increased the liver to body weightratio, but did not significantly alter adrenal, thymus, or spleenweight in the dams. No significant maternal effects were seenat lower doses. The highest doses of both compounds increasedthe incidence of supernumerary ribs in fetuses of treated rats,but did not induce other anomalies. Fetal weight was reducedin rats at the highest dose of bromoxynil octanoate, but noeffects on fetal weight were seen with bromoxynil phenol. Bromoxynilexposure produced a high incidence of supernumerary ribs atmaternally toxic doses in both rats and mice, although no evidenceof maternal stress per se was found. The mechanism and significanceof this effect require further study.     

Preliminary Toxicity Findings in Dogs and Rodents Given the Iron Chelator Ethylenediamine-N,N'-bis(2-hydroxyphenylacetic acid) (EDHPA)

Preliminary Toxicity Findings in Dogs and Rodents Given theIron Chelator Ethylenediamine N,N'-bis(2-hydroxyphenylaceticacid) (EDHPA). ROSENKRANTZ, H., METTERVILLE, J. J., AND FLEISCHMAN,R. W. (1986). Fundam. Appl. Toxicol 6, 292–298. Becauseof a projected pilot study with EDHPA in Cooley's anemia patients,animal studies with emphasis on reversibility of potential toxicsigns were performed. Young dogs were treated iv with 6–18mg/kg or orally with 30–240 mg/kg for 14 days followedby a 16-day recovery period. Drug-induced emesis, elevated BUNchanges in kidney, spleen, and thymus weights diminished duringrecovery. One deceased dog exhibited nephrotoxicity consistingof tubular necrosis and deposition of the iron—EDHPA complex.The latter was observed in the excreta of survivors but kidneydamage was not evident. Atrophy of the spleen and thymus inthe deceased dog was consistent with less intense organ weightchanges in recovered survivors. In the absence of morphologicchanges after recovery, the precise effect on the immune systemis unknown. The iv LD50 was 53 mg/kg for rats and mice. No rodentdeaths occurred at an oral dose of 6000 mg/kg An elevated BUNand changes in kidney, spleen, and thymus weights were confirmedin rodents given iv doses of 5–20 mg/kg or oral dosesof 150–600 mg/kg for 5 days. It is cautioned that duringthe use of EDHPA derivatives that the functions of the renaland immune systems be monitored.     

A Short-Term Feeding Study with Deoxynivalenol (Vomitoxin) Using Rats

A Short-Term Feeding Study with Deoxynivalenol (Vomitoxin) UsingRats. ARNOLD, D. L., KARPINSKI, K. F., MCGUIRE, P. F., NERA,E. A., ZAW1DZKA, Z. Z., LOK, E., CAMPBELL, J. S., TRYPHONAS,L., AND SCOTT, P. M. (1986). Fundam. Appl. Toxicol 6,691–696.Groups of 25 male and 25 female Sprague-Dawley rats were feddiets containing 0, 0.25, 0.5, or 1.0 mg of deoxynivalenol (DON)/kgbody wt for approximately 9 weeks. Each animal's body weightand feed consumption were measured weekly. Upon terminationof the study, each animal's body, heart, liver, spleen, thymus,and kidneys were weighed. A hematological assessment and a 16-parameterserum evaluation were conducted and 8 animals from each groupwere randomly selected to receive tritiated thymidine iv toassess mitotic activity in the esophagus, jejunum, and spleen.A statistically significant, dose-related decrease in body weightgain was observed for all treated females, but only the malesdosed at 1.0 mg/kg were found to have a treatment-related weightgain suppression. The reduced body weight was attributed toa reduced feed consumption. Reductions that were observed inabsolute organ weights, were not apparent after adjusting forbody weight suppression. No dose-related hematological findingswere found. Serum chemistry changes included increased concentrationsof chloride and decreased concentrations of CO₂ and albumin,but only in the females. No histopathological lesions were attributedto DON treatment, but significant decreases in thymidine labelingoccurred in the spleens and jejunums from the males dosed at1.0 mg/kg.     

The in vitro Activation of Cyclophosphamide in the Hydra Developmental Toxicology Assay

The in vitro Activation of Cyclophosphamide in the Hydra DevelopmentalToxicology Assay. Newman, L. M., JOHNSON, E. M., GIACOBBE, R.L., AND FU, L-J. (1990). Fundam. Appl. Toxicol. 15, 488–499.The proteratogen cyclophosphamide (CP) was tested in the HydraAssay in the presence and absence of an in vitro metabolic activationpackage (MAP) consisting of rat hepatic microsomes (0.06 nmolP450/ml), 500 µM NADPH, and 25 µm MgCl. This metabolicsystem was developed through a series of interrelated biochemicaland biological assays to provide maximum cytochrome P450 mixed-functionmonooxygenase (MFO) metabolic capacity while controlling theinherent toxicity of the hepatic preparation and the attendantcofactors. Bioactivation of CP was confirmed under standardhydra assay conditions of pH 7.0 and 20°C and compared withactivation at 37°C. Estimation of total metabolic capacityand verification of activation were made through the appearanceof alkylating metabolites both in the absence and in the presenceof hydra. Chemical exposure was maintained throughout the 92± 2 hr assay with periodic renewal of media (and additives)at 4, 20, 28, 42, and 66 hr of incubation. Inclusion of bioactivationincreased the toxicity of CP by two orders of magnitude. Theminimal affective concentration in the adult and developmentalportions of the assay was decreased from 4000 to 20 µgCP/ml and from 1000 to 4 µg CP/ml, respectively. By limitingthe inherent toxicity of the MFO package, it was possible toavoid pulse-type exposures and ensure that all ontogenic stageswere exposed to active metabolites. The addition of metabolicactivation capacity to an in vitro assay, while not essential,markedly enhances its utility and breadth of application indevelopmental toxicity safety evaluations.     

Maternal and Developmental Toxicity of Chronic Aluminum Exposure in Mice

Maternal and Developmental Toxicity of Chronic Aluminum Exposurein Mice. GOLUB, M. S., GERSHWIN, M. E., DONALD, J. M., NEGRI,S., AND KEEN, C. L. (1987). Fundam. Appl. Toxicol. 8, 346–357.The present study demonstrated aluminum-induced neurotoxicityin mouse dams and developmental retardation in their offspringfollowing oral exposure to several dose levels during gestationand lactation. Female mice fed aluminum lactate (AL) at levelsof 500 or 1000 ppm in their diet from Day 0 gestation to Day21 postpartum were compared to mice which received a 100 ppmaluminum diet either ad libitum or pair-fed to the 1000 ppmAL group. Dams receiving the 500 and 1000 ppm AL diets showedsigns of neurotoxicity beginning at Days 12–15 postpartumand showed significant weight loss. Offspring showed dose-dependentdecreases in body weight (F = 6.47, p < 0.001), crown-rumplength (F = 1.11, p < 0.0001), and ponderal index (F = 6.90,p < 0.0002), at birth and preweaning. Absolute and relativeliver and spleen weights were lower in pups from the high ALgroups compared to controls (F = 3.34, p < 0.025 and F =15.54, p < 0.001, respectively). Neurobehavioral developmentwas somewhat delayed in aluminum-treated pups, but not in theirpair-fed controls (F = 5.52, p < 0.005). In addition to showingoral toxicity of excess AL during development dose-dependenttoxic effects of parenteral aluminum exposure were demonstratedin pregnant mice which were injected subcutaneously with aluminumlactate solution at 10, 20, or 40 mg Al/kg body wt on Days 3,5, 7, 9, 12, 13, and 15 of gestation. Maternal spleen and liverweights were significantly increased in aluminum treated animals(p < 0.001 and p < 0.05, respectively). Fetal crown-rumplengths were significantly reduced in the 20 mg/kg aluminumgroup (F = 9.79, p < 0.001).     

L-Methionine Suppresses Pathological Sequelae of cis-Platinum in the Rat

L-Methionine Suppresses Pathological Sequelae of cis-Platinumin the Rat. BASINGER, M. A., JONES, M. M., AND HOLSCHER, M.A. (1990). Fundam. Appl. Toxicol. 14, 568–577. The pathologicalchanges characteristically observed in the kidney, bone marrow,thymus, spleen, and duodenum of the rat given 12.2 mg/kgofc/5-platinum(CDDP)ipare reduced or eliminated when a CDDP solution containing a20-fold excess of L-methionine to c/s-platinum is administered.L-Methionine was also effective in reducing the renal toxicityinduced by CDDP when given orally 20 min before the iv administrationof 7.5 mg CDDP/kg. L-Methionine did not compromise the efficacyof CDDP when the antitumor activity of the combination of L-methio-nineand CDDP was measured against the Walker 256 carcinosarcomain the rat. No significant reduction in the antitumor activityof the CDDP resulted from the parenteral administration of L-Methioninewhen evaluated against the L1210 murine leukemia. The oral administrationof L-methionine (500 mg/kg) 30 min after the administrationof CDDP has no significant effect on the antitumor activityof CDDP in mice bearing the L1210 murine leukemia. The resultssuggest that L-methionine may have some practical utility inthe control of certain aspects of CDDP toxicity.     

Evaluation of OECD screening tests 421 (reproduction/developmental toxicity screening test) and 422 (combined repeated dose toxicity study with the reproduction/developmental toxicity screening test)

The Advisory Committee on Existing Chemicals (BUA) of the Federal Republic of Germany convened a panel with expertise in reproductive and developmental toxicology to evaluate the OECD Screening Tests 421 (Reproduction/Developmental Toxicity Screening Test) and 422 (Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test) with respect to their ability to unmask any potential toxic effects on reproduction. The original assignment for that panel was to "validate" those screening tests. However, the panel members recognized beforehand that this was actually an impossible task because of lack of a sufficient database. Only five chemicals with known reproductive toxicity had been examined following the OECD Screening Test Guidelines 421 or 422. A comparison of these test results with those of the definitive OECD Test Guidelines 414, 415, 416, or additional investigations could, therefore, only have been made with this very limited number of chemicals that had also undergone evaluation by one of the test guidelines cited. In each case biological properties relevant to reproductive toxicity were also indicated by the OECD Screening Tests 421 or 422. This communication reviews the main differences in study design of OECD Screening Test Guidelines 421 and 422 compared to those definitive test guidelines of similar study design for reproduction or developmental toxicity (especially with the one-generation study, OECD Test Guideline 415). The very limited possibilities of detecting late postnatal and postlactational manifestations are emphasized, as is the low statistical power of the OECD Screening Tests 421 and 422. Furthermore, the very limited ability to unmask teratogenicity is delineated. The outcome of screening tests was evaluated based on the results of 57 studies conducted according to the OECD Test Guideline 421 or 422. The test results were categorized according to the incidence of toxic effects on reproduction in the parent animals or their offspring and related to general toxic effects. Based on the ranking of these results, recommendations regarding setting rational priorities for further evaluations of existing chemicals' reproductive hazards are made. In general, the reviewer panel supports the OECD position that the screening tests are useful for initial hazard assessment and can contribute to the decision-making process on setting priorities for further test requirements. The panel also agrees with the OECD statement that the OECD Screening Tests 421 and 422 are neither an alternative to definitive tests (i.e., OECD Test Guidelines 414, 415, and 416) nor are they intended as their replacement.     

Evaluation of the Reproductive Toxicology of 2,4,6-Trichiorophenol in Male and Female Rats

Evaluation of the Reproductive Toxicology of 2,4,6-Trichlorophenolin Male and Female Rats. BLACKBURN, K., ZENICK, H., HOPE, E.,MANSON, J. M., GEORGE, E. L., AND SMITH, M. K. (1986). Fundam.Appl. Toxicol. 6, 233–239. The toxicity of chlorinatedorganic compounds which may be generated as a by-product ofdrinking water chlorination has been an issue of increasingconcern. Relatively few data are available concerning theirreproductive toxicity. The present study was designed to evaluatethe reproductive effects of one of these compounds, 2,4,6-trichlorophenol(TCP), in male and female rats. Adult males were treated witheither 0, 100. 500, or 1000 mg/kg of TCP (po) for 10 weeks,at which time semen evaluations were conducted on ejaculatesrecovered from the genital tract of receptive females. Fertilitywas assessed in the 0- and 1000-mg/kg groups. Females were treatedwith identical doses for 2 weeks prior to pregnancy then throughoutgestation. Dams were allowed to litter and pup development wasmonitored until Day 42 postpartum. TCP had no effect on anysperm parameter or male fertility. Treatment of females with1000 mg/kg of TCP produced gross maternal toxicity as reflectedin increased lethality and decreased weight gains in the dams.However, no treatment-related differences were seen in littersizes or pup survival. Male and female birth weights were significantlydepressed in the 500- and 1000-mg/kg groups; these differencesdisappeared by Day 4 postpartum, suggesting that they were areflection of maternal toxicity. To this extent, the reproductiveprocesses of male and female rats do not appear to be a primarytarget for the effects of TCP.     

An Immunotoxicological Evaluation of 4, 4'-Thiobis-(6-t-butyl-m-cresol) in Female B6C3F1 Mice: 1. Body and Organ Weights, Hematology, Serum Chemistries, Bone Marrow Cellularity, and Hepatic Microsomal Parameters

An Immunotoxicological Evaluation of 4,4'-Thiobis-(6-t-butyl-m77-cresol)in Female B6C3F1 Mice. 1. Body and Organ Weights, Hematology,Serum Chemistries, Bone Marrow Cellularity, and Hepatic MicrosomalParameters. MUNSON, A. E., WHITE, K. L., JR., BARNES, D. W.,MUS-GROVE, D. L., LYSY, H. H., AND HOLSAPPLE, M. P. (1988).Fundam. Appl. Toxicol. 10, 691–700. Adult female B6C3F1mice were gavaged with 4,4'-thiobis-(6-t-butyl-m-cresol) (TBBC)in corn oil at doses of 10, 100, or 200 mg/kg daily for 14 consecutivedays. There was no overt toxicity, as manifested by grosslyobservable behavioral changes, decreased growth rate over theexposure period, or mortality. There were also no marked effectson serum chemistries or hematology, with the exception of asignificant increase (41%) in the number of leukocytes at thehighest dose. Absolute differential counts indicated that significantincreases occurred in the number of lymphocytes (31%) and neutrophils(177%). Studies with bone marrow indicated a significant 30%increase in the number of cells/femur from animals treated withthe highest dose of TBBC. The number of macrophage progenitors(CFU-M)/femur was significantly increased by 28%, while thenumber of granulocyte-monocyte progenitors (CFU-GM)/femur wasnonsig-nificantly increased by 20% in the high dose animals.The weight of both the spleen and liver was increased in a dose-relatedfashion, although the histopathology of the spleen of TBBC-treatedmice was not different from control. The livers of mice receivingthe high dose showed mild focal hydropic degeneration, mildhepatitis, and a slight increase in the number of Kupffer cells.No other organs were affected. Liver microsomal protein andcytochrome P-450 levels were increased in a dose-related fashion.Enzyme activities of aminopyrine demethylase and aniline hydroxylase,but not arylhydrocarbon hydroxylase, were also increased ina dose-related fashion.     

Toxicity evaluation of petroleum blending streams: reproductive and developmental effects of light catalytic cracked naphtha distillate in rats

A distillate of light catalytic cracked naphtha (CAS number 64741-55-5, LCCN-D), administered by inhalation, was tested for reproductive and developmental toxicity in Sprague-Dawley rats, following a modified OECD Guideline 421, Reproductive/Developmental Toxicity Screening Protocol. LCCN-D was administered as a vapor, 6 h/d, 7 d/wk at target concentrations of 0, 750, 2500 or 7500 ppm to female rats for approximately 7 wk from 2 wk prior to mating, during mating through gestational d 19, and to males beginning 2 wk prior to mating for 8 consecutive weeks. Dams and litters were sacrificed on postnatal d 4, and males were sacrificed within the following week. Parental systemic effects observed at the 7500 ppm exposure level were increased kidney weights and relative liver weights in males and increased spleen weights in high-dose females. Livers and spleens from rats in the high-dose group were normal in appearance at necropsy. IncreaSed kidney weights in high-dose males were indicative of male-rat-specific light hydrocarbon nephropathy. No test-related microscopic changes were observed in the reproductive organs or nasal turbinate tissues of either sex. Reproductive performance was unaffected by treatment with LCCN-D. Fertility index was > or =90% in all dose groups. There were no exposure-related differences in implantation sites and live pups per litter, and no gross abnormalities were observed. Pups born from treated dams showed comparable body weights and weight gains to controls. The viability index on postpartum d 4 was > or =97%; the high-dose group had more male than female pups at birth and at d 4 postpartum. Under the conditions of this study, the no-observable-adverse-effect level (NOAEL) for exposure to light catalytic cracked naphtha distillate for parental toxicity was 2500 ppm and the NOAEL for reproductive performance and developmental toxicity was 7500 ppm.     

Percutaneous Absorption, Metabolism, and Hemolytic Activity of n-Butoxyethanol

Percutaneous Absorption, Metabolism, and Hemolytic Activityof n-Butoxyethanol. BARTNIK, F. G., REDDY, A. K., KLECAK, G.,ZIMMERMANN, V., HOSTYNEK, J. J., and KUNSTLER, K. (1987). Fundam.Appl. Toxicol. 8, 59–70. A series of studies was conductedto examine the percutaneous absorption, distribution, excretion,and hemolytic activity of n-butoxyethanol (BE). Rats receivinga subcutaneous dose of ¹⁴C-labeled BE excreted the radioactivityin the urine (79%), expired air (10%), and feces (0.5%) within72 hr. Of the organs analyzed, thymus and spleen showed elevatedspecific radioactivities as compared with blood. A percutaneousapplication of BE on rats, under nonocclusive conditions, showed25–29% absorption within 48 hr. Peak blook levels of BEoccurred at 2 hr after application; butoxyacetic acid (BAA)was found to be the major metabolite. Comparison of in vitroskin penetration data showed the following absorption patternof BE: hairless rat >> pig > human skin. Hemolysisand associated hematological changes were noted in the ratswhich received single dermal applications of 260–500 mg/kgof BE. In vitro, BAA showed markedly greater hemolytic abilityon rat erythrocytes than did BE. Human erythrocytes showed nohemolysis when incubated with BE or BAA at concentrations thatare hemolytic to rat erythrocytes. An intravenous dose of 62.5mg/kg of BE does not result in hemolysis or hemoglobinuria inthe rat. The rat may be an animal model with increased susceptibilityto the effects of BE compared with humans because of its rapidpercutaneous absorptive ability and its greater hemolytic sensitivity.     

Evaluation of the Primary Humoral Immune Response Following Exposure of Male Rats to 17 {beta}-Estradiol or Flutamide for 15 Days

There is a concern that certain industrial chemicals found inthe environment may mimic or antagonize endogenous hormonesand adversely affect the endocrine as well as the immune system.The objective of this study was to determine if exposure ofCrl:CD (SD)BR male rats to 17ß-estradiol (17ß-E2),an estrogen receptor agonist, or flutamide (FLUT), an androgenreceptor antagonist, would significantly alter the primary IgMhumoral immune response to sheep red blood cells (SRBC). Thisstudy was conducted in the context of a male in vivo Tier Ibattery designed to identify endocrine-active compounds (EACs).The Tier I male battery consists of organ weights coupled witha comprehensive hormonal assessment Rats were dosed by the intraperitonealroute for 15 days with vehicle or 0.001, 0.0025, 0.0075, or0.050 mg/kg/day 17ß-E2 or 0.25, 1, 5, or 20 mg/kg/dayFLUT. Six days prior to termination, selected rats were injectedintravenously with SRBC for assessment of humoral immune function.Spleen cell number and spleen and thymus weights were obtained.Serum was analyzed for anti-SRBC IgM antibody by using an enzyme-linkedimmunosorbent assay. At 0.050 mg/kg/day 17ß-E2, meanfinal body and absolute thymus weights were significantly decreasedto 84 and 65% of control, respectively. 17ß-E2 didnot significantly alter spleen weight, spleen cell number, orthe primary IgM humoral immune response to SRBC. The no-observed-adverse-effectlevel (NOAEL) for immune system alteration was 0.050 mg/kg/day17B-E2 since the decrease in absolute thymus weight was judgedto be secondary to the decrements in body weight. In the TierI male battery, responses to 17ß-E2 included decreasedabsolute testis and epididymis weights, decreased relative accessorysex gland unit weights, hormonal alterations (decreased serumtestosterone (T), dihydrotestosterone (DHT), and luteinizinghormone (LH), and increased serum prolactin and E2 levels).The lowest-observed-adverse-effect level (LOAEL) for the reproductiveindices was 0.001 mg/kg/day 17ß-E2 based on the hormonalalterations seen at this level; no NOAEL was established. Exposureto FLUT did not significantly alter mean final body, spleen,or absolute thymus weights, spleen cell number, or the primaryIgM humoral immune response to SRBC. A significant increase(118% of control) in relative thymus weight was observed at20 mg/kg/ day FLUT. The NOAEL for immune system alteration was5 mg/kg/day FLUT based on the increased relative thymus weightsthat were judged to be compound-related. In the Tier I malebattery, responses to FLUT included decreased absolute epididymisand relative accessory sex gland unit weights and hormonal alterations(increased serum T, DHT, E2, and LH, and decreased folliclestimulating hormone levels). The LOAEL for the reproductiveindices was 0.25 mg/kg/day FLUT based on the hormonal alterationsseen at this level; no NOAEL was established. Based on thesedata, the reproductive and not the immune system appears tobe the primary target organ of toxicity in young adult malerats treated with either 17ß-2 or FLUT.     

TOXICITY EVALUATION OF PETROLEUM BLENDING STREAMS: REPRODUCTIVE AND DEVELOPMENTAL EFFECTS OF LIGHT CATALYTIC CRACKED NAPHTHA DISTILLATE IN RATS

A distillate of light catalytic cracked naphtha (CAS number 64741-55-5, LCCN-D), administered by inhalation, was tested for reproductive and developmental toxicity in Sprague-Dawley rats, following a modified OECD Guideline 421, Reproductive/ Developmental Toxicity Screening Protocol. LCCN-D was administered as a vapor, 6 h/ d, 7 d/wk at target concentrations of 0, 750, 2500 or 7500 ppm to female rats for approximately 7 wk from 2 wk prior to mating, during mating through gestational d 19, and to males beginning 2 wk prior to mating for 8 consecutive weeks. Dams and litters were sacrificed on postnatal d 4, and males were sacrificed within the following week. Parental systemic effects observed at the 7500 ppm exposure level were increased kidney weights and relative liver weights in males and increased spleen weights in highdose females. Livers and spleens from rats in the high-dose group were normal in appearance at necropsy. Increased kidney weights in high-dose males were indicative of male-rat-specific light hydrocarbon nephropathy. No test-related m icroscopic changes were observed in the reproductive organs or nasal turbinate tissues of either sex. Reproductive performance was unaffected by treatment with LCCN-D. Fertility index was 90% in all dose groups. There were no exposure-related differences in implantation sites and live pups per litter, and no gross abnormalities were observed. Pups born from treated dams showed comparable body weights and weight gains to controls. The viability index on postpartum d 4 was 97% ; the high-dose group had more male than female pups at birth and at d 4 postpartum. Under the conditions of this study, the no-observable-adverse-effect level (NOAEL) for exposure to light catalytic cracked naphtha distillate for parental toxicity was 2500 ppm and the NOAEL for reproductive performance and developmental toxicity was 7500 ppm.     

Target Tissue Morphology and Serum Biochemistry following 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) Exposure in a TCDD-Susceptible and a TCDD-Resistant Rat Strain

Target Tissue Morphology and Serum Biochemistry following 2,3,7,8-Tetrachlorodibenzo-p-dioxin(TCDD) Exposure in a TCDD-Susceptible and a TCDD-Resistant RatStrain. POHJANVIRTA, R., KULJU, T., MORSELT, A. F. W., TUOMINEN,R., JUVONEN, R., ROZMAN, K.,MÄNNISTÖ, P., COLLAN,Y., SAINIO, E.-L., AND TUOMISTO, J. (1989). Fundam. Appl. Toxicol.12, 698–712. The mode of action of the highly toxic environmentalcontaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is unknown.It was recently discovered that two strains of rat, Long-Evans(L-E) and Han/Wistar (H/W), differ widely in susceptibilityto TCDD. Employing this strain divergence as a probe, the presentstudy set out to assess the role of various biochemical andmorphological effects in TCDD lethality. In the main experiment,the rats were treated once ip with 0, 5, 50, or (H/W) 500 µg/kgTCDD and killed 1 to 16 days postexposure. Several target organswere evaluated by light microscopy and a number of serum lipidand carbohydrate parameters as well as a few major regulatoryhormones were analyzed. The results demonstrated that most alterationscaused by TCDD were essentially similar in both strains. TCDDreduced circulating thyroxine to a slightly greater extent andmore permanently in the sensitive L-E strain. Moreover, a highlysignificant interaction on thyroid-stimulating hormone was foundamong strain, dose. and time. Serum concentrations of corticosteroneand free fatty acids were increased only in the L-E rats given50 µg/kg TCDD, i.e., at an apparent LDl00 dose level forthis strain. Yet, the most striking interstrain difference wasseen in the liver which was distinctly affected after Day 4in L-E rats given 50 µg/kg TCDD but only marginally affectedin rats from any H/W group. The lesion, while showing no necroticcell changes, was suggestive of plasma membrane damage, possiblyreflecting the production of free radicals. The relation ofthe findings to possible mechanisms of TCDD action is discussed.     

Two-Week, Repeated Inhalation Exposure of F344/N Rats and B6C3F Mice to Ferrocene

Two-Week, Repeated Inhalation Exposure of F344/N Rats and B6C3F¹Mice to Ferrocene. SUN, J. D., DAHL, A. R., GILLETT, N. A.,BARR, E. B., CREWS, M. L., EIDSON, A. F., BECHTOLD, W. E., BURT,D. G., DIETER, M. P., AND HOBBS, C. H. (1991). Fundam. ApplToxicol. 17, 150-158. Ferrocene (dicyclopentadienyl iron; CASNo. 102-54-5) is a relatively volatile, organometallic compoundused as a chemical intermediate, a catalyst, and as an antiknockadditive in gasoline. It is of particular interest because ofits structural similarities to other metallocenes that havebeen shown to be carcinogenic. F344/N rats and B6C3F, mice wereexposed to 0, 2.5, 5.0, 10, 20, and 40 mg ferrocene vapor/m3,6 hr/day for 2 weeks. During these exposures, there were nomortality and no observable clinical signs of ferrocene-relatedtoxicity in any of the animals. At the end of the exposures,male rats exposed to the highest level of ferrocene had decreasedbody-weight gains relative to the weight gained by filteredair-exposed control rats, while body-weight gains for all groupsof both ferrocene- and filtered air-exposed female rats weresimilar. Male mice exposed to the highest level of ferrocenealso had decreased body-weight gains, relative to controls,while female mice had relative decreases in body-weight gainsat the three highest exposure levels. Male rats had a slightdecrease in relative liver weight at the highest level of exposure,whereas no relative differences in organ weights were seen infemale rats. Male mice had exposure-relative decreases in liverand spleen weights, and an increase in thymus weights, relativeto controls. For female mice, relative decreases in organ weightswere seen for brain, liver, and spleen. No exposure-relatedgross lesions were seen in any of the rats or mice at necropsy.Histopathological examination was done only on the nasal turbinates,lungs, liver, and spleen. The only exposure-related findingwas histopathologic lesions in the nasal turbinates of bothspecies. These lesions were primarily centered in the olfactoryepithelium and were morphologically diagnosed as subacute, necrotizinginflammation. Nasal lesions were observed in all ferrocene-exposedanimals and differed only in severity, which was dependent onthe exposure concentration. In vitro metabolism studies of ferroceneshowed that nasal tissue, particularly the olfactory epithelium,had 10 times higher "ferrocene hydroxylating" activity thandid liver tissue from the same animals. These results suggestthat the mechanism of ferrocene toxicity may be the intracellularrelease of ferrous ion through ferrocene metabolism, followedby iron-catalyzed lipid peroxidalion of cellular membranes.     

Acute Toxicity of Helenalin in BDF1 Mice

Acute Tyyoxicity of Helenalin in BDF1 Mice. CHAPMAN, D. E.,ROBERTS, G. B., REYNOLDS, D. J., GRIPPO, A. A., HOLBROOK, D.J., HALL, I. H., CHANEY, S. G., CHANG, J., AND LEE, K. H. (1988).Fundam. Appl. Toxicol 10, 302-312. The acute toxicity of helenalin,a sesquiter-pene lactone isolated from Helenium microcephalum,was examined in male BDF1 mice. The 14-day LD50 for a singleip dose of helenalin in male mice was 43 mg/kg. A single ipinjection of 25 mg helenalin/kg increased serum alanine aminotransferase(ALT), lactate dehydrogenase (LDH), urea nitrogen (BUN), andsorbitol dehydrogenase within 6 hr of treatment. Multiple helenalinexposures, ip injection of 25 mg helenalin/kg for 3 days, increaseddifferential poly-morphonuclear leukocyte counts and decreasedlymphocyte counts. Serum ALT, BUN, and cholesterol levels werealso increased by multiple helenalin exposures at 25 mg helenalin/kg/day. Helenalin significantly reduced liver, thymus, and spleenrelative weights and histologic evaluation revealed substantialeffects of multiple helenalin exposures on lymphocytes of thethymus, spleen, and mesenteric lymph nodes. No helenalin-inducedhistologic changes were observed in the liver or kidney. Multiplehelenalin exposures (25 mg/kg/day) significantly inhibited hepaticmicrosomal enzyme activities (aminopyrine demethylase and anilinehydroxylase) and decreased microsomal cytochromes P-450 and65 contents. Three concurrent days of diethyl maleate (DEM)pretreatment (3.7 mmol DEM/kg, 0.5 hr before helenalin treatment)significantly increased the toxicity of helenalin exposure.The present studies indicate that the hepatic microsomal drugmetabolizing system and lymphoid organs are particularly vulnerableto the effects of helenalin. In addition, helenalin toxicityis increased by DEM pretreatments which have been shown to decreaseglutathione concentrations.     

Genotoxic Properties of Haloacetonitriles: Drinking Water By-Products of Chlorine Disinfection

Genotoxic Properties of Haloacetonitriles: Drinking Water By-Productsof Chlorine Disinfection. DANIEL, F. B., SCHENCK, K. M., MATTOX,J. K., LIN, E. L. C., HAAS, D. L., AND PEREIRA, M. A. (1986).Fundam. Appl. Toxicol. 6,447–453. Chlorinated and brominatedhaloacetonitriles (HAN), known drinking water contaminants whichform during chlorine disinfection, were investigated for genotoxicactivity. The HAN produced DNA strand breaks in cultured humanlymphoblastic (CCRF-CEM) cells, bound to the nucleophilic trappingagent 4-(p-nitrobenzyl)pyridine and formed a covalent bond topolyadenylic acid in a cell-free reaction system. Thus, we havedemonstrated that these chemicals are genotoxic, which wouldindicate a potential for carcinogenic activity and for humanhealth hazard.     

Pharmacological and Toxicological Properties of Arotinoids SMR-2 and SMR-6 in Mice

Pharmacological and Toxicological Properties of Arotinoids SMR-2and SMR-6 in Mice. LINDAMOOD, C, III, COPE, F. O., DILLEHAY,D. L., EVERSON, M. P., GILES, H. D., LAMON, E. W., MCCARTHY,D. J., SARTIN, J. L., AND HILL, D. L. (1990). Fundam. Appl.Toxicol. 14, 15–29. Studies were conducted to define primarypharmacological and toxicological properties of two arotinoids,SMR-2 and SMR-6, in male B6D2F1 mice. Mice were gavaged dailyfor up to 22 days with retinoids in corn oil (0.1, 0.2, or 0.4mg/kg day SMR-2 or SMR-6 or 2.5, 10, or 30 mg/kg all-trans-retinoicacid as a reference control). Toxicological and biochemicalend-points were assayed after 8, 15, and 22 days. At toxic doses,i.e., those inducing weight loss, morphological changes wereobserved in skin, lymph nodes, spleen, bone marrow, liver, thymus,forestomach, adrenal, bone, and testes. Biochemical alterationsincluded elevated serum alkaline phosphatase, corticosterone,and interleukins–1, –2, and –3. Additionalimmune alterations included increased responsiveness of spleencells to both thymus-dependent and thymus-inde-pendent mitogensand increases in the total number of B cells in the spleen.At doses not inducing weight loss, target organ effects includedthe appearance of plasma cells and infiltration of polymorphonuclearcells in lymph nodes; myeloid cell hypercellularity in bonemarrow, hema-topoiesis in spleen; subacute inflammation in forestomach;and periportal cytoplasmic vacuo-lization in liver. At the lowdoses, SMR-2 resulted in decreased responsiveness of spleencells to mitogens and SM R-6 caused increased responsiveness.SMR-6 also increased interleukin-1 and -2 production at lowdoses. Biochemical effects included reduced activities of liveraryl hydrocarbon hydroxylase (AHH) and soluble brain proteinkinase C. Overall, the results suggest that leukcopoiesis andreduced liver AHH and reduced soluble protein kinase C activitiesare the primary and initial pharmacological and toxicologicaleffects of retinoids.     

Effect of Acute Propanil Exposure on the Immune Response of C57BI/6 Mice

Effect of Acute Propanil Exposure on the Immune Response ofC57BI/6 Mice. BARNETT, J. B., AND GANDY, J. (1989). Fundam.Appl. Toxicol. 12, 757–764. Propanil is a herbicide thatis used extensively in rice farming to kill weeds without damagingthe rice plant The immunotoxic effects of acute exposure topropanil were determined in adult C57B1/6 female mice exposedintraperitoneally to propanil at doses of 0, 10, 25, 50, 100,200,or 400 mg/kg body wt. One week following exposure, the immunecompetency of the animals was assessed. Contact hypersensitivityresponse (CHR), blastogenic response to T- and B-cell-specificmitogens, and mixed lymphocyte reaction (MLR) were significantlydepressed only in propanil-treated animals at 400 mg/kg. However,the number of splenic antibody-producing cells was also significantlydepressed in a dose-dependent manner at the lower doses of 50,100, and 200 mg/kg. In addition, a significant reduction inthe thymus weight and an increase in absolute and relative spleenweight were also measured in animals treated with 200 and 400mg/kg. The increase in spleen weight also showed a concomitantrise in spleen cellularity. These data indicate that propanilhas a dose-dependent immunotoxic effect on the adult mouse thataffects primarily the humoral response     

Reproductive Toxicity of Three Phthalic Acid Esters in a Continuous Breeding Protocol

Reproductive Toxicity of Three Phthalic Acid Esters in a ContinuousBreeding Protocol. HEINDEL, J. J., GULATI, D. K., MOUNCE, R.C., RUSSELL, S. R., AND LAMB, J. C., IV. (1989), Fundam. ApplToxicol. 12, 508–518. A continuous breeding protocol wasutilized to examine the reproductive toxicity of three phthalateesters. CD-1 mice were given diets with either di-n-propyl phthalate(DPrP:0.0, 1.25, 2.5, or 5.0%), di-n-pentyl phthalate(DPP:0.0,0.5,1.25, or 2.5%), or di-n-octyl phthalate (DOP: 0.0, 1.25, 2.5,or 5.0%). Both male and female mice (20 pairs per treatmentgroup. 40 pairs of control animals) were dosed for 7 days priorto and during a 98-day cohabitation period. Reproductive functionwas evaluated during the cohabitation period by measuring numberof litters per pair, live pups per litter, and pup weight. Therewas no apparent effect on reproductive function in the animalsexposed to DOP at dose levels sufficient to cause a significantincrease in liver weight. Both DPP and DPrP were toxic to thereproductive system as evidenced by a complete inhibition offertility at 1.25 and 2.5% DPP or 5.0% DPrP, and reduced fertility(litters/pair and live pups/litter, 0.5% DPP; live pups/litter,2.5% DPrP). Toxicity of DPP had a strong male component andfemale component, whereas DPrP was more toxic to the femalethan the male reproductive system. DPP and DPrP treatment wasassociated with decreased body weight, increased liver weight,decreased testis and epididymis weights, decreased epididymalsperm concentration, and elevated seminiferous tubule atrophy.A comparison of seven phthalate esters tested using this continuousbreeding protocol indicates the relative order of reproductivetoxicity as diethylhexyl, dihexyl, dipentyl, dibutyl, dipropyl;diethyl and dioctyl are nontoxic.