Oral and dermal developmental toxicity studies of phenylethyl alcohol in rats.

Phenylethyl alcohol (PEA) was tested for developmental toxicity. Pregnant rats were fed 0, 83, 266, or 799 mg/kg/d PEA on gestation days (GDs) 6 to 15; only minimal, nonsignificant effects were observed. In dermal studies, PEA (neat) was applied to the skin on GDs 6 to 15 at dosages of 0, 140, 430, or 1400 mg/kg/d and at 0, 70, 140, 280, 430, or 700 mg/kg/d in a corroborative study. Observations included maternal and embryo-fetal toxicity/abnormalities at 1400 mg/kg/d, increased incidences of rudimentary cervical ribs at ≥430 mg/kg/d, and reduced fetal body weights at ≥140 mg/kg/d. Dermal maternal and developmental no-observed-adverse-effect levels are 70 mg/kg/d, based on dermal irritation and reductions (nonsignificant) in fetal body weights. Human exposure from fragrances is 0.02 mg/kg/d, resulting in a margin of safety >2600, when marked differences in dermal absorption between rats and humans are considered. Under normal fragrance use conditions, PEA is not a developmental toxicity hazard for humans.

The pharmacokinetics of phenylethyl alcohol (PEA): safety evaluation comparisons in rats, rabbits, and humans.

The present studies were conducted to compare the dermal absorption, plasma pharmacokinetics, and excretion of phenylethyl alcohol (PEA) by pregnant and nonpregnant rats, rabbits, and humans. The PEA is a natural fragrance material that is widely used in perfumes, soaps, and lotions and is a major ingredient of natural rose oil. Following dermal (430, 700, or 1400 mg/kg body weight [bw]), gavage (430 mg/kg bw), or dietary (430 mg/kg bw) administration of PEA to rats, plasma concentrations of PEA were found to be low regardless of the route of administration. The plasma concentrations of phenylacetic acid (PAA, the major metabolite of PEA) greatly exceeded the concentrations of PEA and were highest after gavage, followed by dermal then dietary administration. Absorption, distribution, metabolism, and excretion were compared following topical application of ¹4C-labeled PEA to rats, rabbits, and humans (specific activities of dosing solutions: 58-580, 164, and 50 µCi/mL, respectively). In rabbits, the plasma concentration-time profile for PAA was markedly prolonged compared to rats or humans. In humans, only 7.6% of the applied dose of PEA was absorbed, versus 77% in rats and 50% in rabbits. Based on a human dermal systemic exposure of 0.3 mg/kg per day from the use of multiple consumer personal care products containing PEA, a rat dermal no observed adverse effect level of 70 mg/kg per day, and the percentage of dose absorbed in humans, the margin of safety exceeds 2600 concluding that, under normal fragrance use conditions, PEA is not a developmental toxicity hazard for humans.

Uterotrophic assay of percutaneous lavender oil in immature female rats.

The estrogenic potential of lavender oil was evaluated in a percutaneous uterotrophic bioassay in immature female rats. Four groups of 10 immature female rats each were randomly selected on postpartum day (PPD) 16. During the 3-day treatment period (PPDs 19-21), the immature rats were separated from the dams, caged in groups of 5 in a litter box for 6 hours, and administered the vehicle control article (corn oil) or lavender oil at 20 or 100 mg/kg per day. All dosages were administered as a 5 mL/kg volume in a Hilltop Chamber (25 mm diameter; absorbent material removed) placed on the shaved back of each immature rat, and secured with micropore tape and Vetrap. A positive control group was gavaged twice daily with 2.5 µg/kg per day of 17α-ethinyl estradiol. Daily observations included viability, clinical signs, body weights, and body weight gains. All rats were euthanized 24 hours after the third and final treatment, the uteri and ovaries were removed, and the paired ovaries and wet and blotted uterine weights were recorded. No unscheduled deaths occurred. No skin reactions were observed. Both dosages of lavender oil significantly reduced body weight gains after the third day of treatment, but terminal body weights and mean absolute and relative uterine weights did not differ significantly from vehicle control values. Positive controls showed significant increases in body weight and increased mean absolute and relative uterine weights as expected. Based on these data, lavender oil, at dosages of 20 or 100 mg/kg, was not active in the rat uterotrophic assay and gave no evidence of estrogenic activity.

Evaluation of the reproductive and developmental risks of caffeine.

A risk analysis of in utero caffeine exposure is presented utilizing epidemiological studies and animal studies dealing with congenital malformation, pregnancy loss, and weight reduction. These effects are of interest to teratologists, because animal studies are useful in their evaluation. Many of the epidemiology studies did not evaluate the impact of the "pregnancy signal," which identifies healthy pregnancies and permits investigators to identify subjects with low pregnancy risks. The spontaneous abortion epidemiology studies were inconsistent and the majority did not consider the confounding introduced by not considering the pregnancy signal. The animal studies do not support the concept that caffeine is an abortafacient for the wide range of human caffeine exposures. Almost all the congenital malformation epidemiology studies were negative. Animal pharmacokinetic studies indicate that the teratogenic plasma level of caffeine has to reach or exceed 60 µg/ml, which is not attainable from ingesting large amounts of caffeine in foods and beverages. No epidemiological study described the "caffeine teratogenic syndrome." Six of the 17 recent epidemiology studies dealing with the risk of caffeine and fetal weight reduction were negative. Seven of the positive studies had growth reductions that were clinically insignificant and none of the studies cited the animal literature. Analysis of caffeine's reproductive toxicity considers reproducibility and plausibility of clinical, epidemiological, and animal data. Moderate or even high amounts of beverages and foods containing caffeine do not increase the risks of congenital malformations, miscarriage or growth retardation. Pharmacokinetic studies markedly improve the ability to perform the risk analyses.

Evaluation of the developmental toxicity of dihydromyrcenol in rats.

Dihydromyrcenol, a widely used fragrance ingredient, was evaluated for developmental toxicity in pregnant Sprague-Dawley rats (25/group). Oral dosages of 0, 250, 500, or 1000 mg/kg/d in corn oil were administered on gestational days 7 to 17. Rats were observed for viability, clinical signs, body weights, and feed consumption. Caesarean sectioning and necropsy occurred on gestational day 21. Fetuses were weighed and examined for sex, gross external changes, and soft tissue or skeletal alterations. All rats survived until scheduled termination. No clinical signs were attributed to dihydromyrcenol. There were no gross tissue changes at necropsy. The 1000-mg/kg/d dosage group had reduced mean maternal body weight gains of 5% compared with controls, whereas absolute and relative feed consumption were significantly reduced during the dosage period. This threshold systemic maternal toxicity was associated with threshold developmental toxicity in the 1000-mg/kg/d dosage group. Fetal effects included a minimal approximately 3% reduction in fetal body weight; reversible variations in ossification, including retarded ossification of the metatarsal bones in the hindpaws; and an increase in supernumerary thoracic ribs with associated increases or decreases in thoracic and lumbar vertebrae, respectively. Based on these data, maternal and developmental no observable effect levels of 500 mg/kg/d and maternal and developmental no observable adverse effect levels of 1000 mg/kg/d were established for dihydromyrcenol. It was concluded that dihydromyrcenol is not a selective developmental toxicant in rats under the conditions of this study and that a margin of safety of 25 000 exists between reversible developmental delays in rats and the estimated daily human exposure level of 0.02 mg/kg/d.

Evaluation of the developmental toxicity of 1-(1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethyl-2-naphthalenyl) ethanone (OTNE) in rats.

The developmental toxicity of 1-(1,2,3,4,5,6,7,8-Octahydro-2,3,8,8-tetramethyl-2-naphthalenyl) ethanone (OTNE), a widely used fragrance ingredient, was evaluated in pregnant Sprague-Dawley rats (25/group) gavaged with dosages of 0 (water), 96, 240, or 480 mg/kg/d on days 7 through 17 of gestation (GDs 7-17). Rats were observed for clinical signs, abortions, premature deliveries, body weights, and feed intake. Caesarean section and necropsy were performed on GD 21. Fetuses were weighed and examined for gender, gross external changes, and soft tissue or skeletal alterations. No deaths or premature deliveries were attributed to OTNE. OTNE-related clinical signs included significantly increased incidences of excessive salivation in all 3 treatment groups, and urine-stained abdominal fur in the high dosage group. Mean body weight gains were significantly reduced by all OTNE dosages on GDs 7-10, while at 480 mg/kg/d, significant reductions continued through the remainder of the dosage period. Feed consumption generally paralleled body weight gains. Fetal body weights were reduced by 480 mg/kg/d, but not to a statistically significant degree. No fetal gross external, soft tissue, or skeletal malformations or variations were attributable to OTNE. Based on these data, maternal and developmental no-observable-adverse-effect-levels (NOAELs) of 240 mg/kg/d were established for OTNE. It was concluded that OTNE is not a developmental toxicant in rats under the conditions of this study, and that a margin of safety greater than 2700 exists between reversible developmental delays in rats and the calculated daily human exposure level of 0.086 mg/kg/d.

Neither antibody to a group B streptococcal conjugate vaccine nor the vaccine itself is teratogenic in rabbits.

Group B Streptococcus (GBS) is a leading cause of human neonatal bacterial disease, resulting in pneumonia, sepsis, meningitis and sometimes, death. Supportive preclinical studies of GBS capsular polysaccharide (CPS)-protein conjugate vaccines have led to several phase 1 and phase 2 trials in healthy, non-pregnant adults, which demonstrated that the vaccines, produced at the Channing Laboratory, were safe and immunogenic. However, evaluation of the safety and immunogenicity of a GBS conjugate vaccine administered to pregnant women demanded that it be manufactured under current good manufacturing practices (cGMP) and that it undergo developmental toxicity evaluation. In this report, we describe a GBS type III CPS-tetanus toxoid (III-TT) vaccine lot 3-1-96 manufactured and vialed under cGMP and our evaluation of the effect of this vaccine and of GBS type III CPS-specific antibody on conception and early- and late-stage fetal development in rabbits. III-TT lot 3-1-96 was compositionally similar to prototype III-TT lot 91-1, produced under non-GMP, and was potent in a mouse maternal vaccination-neonatal pup challenge model of GBS disease. Four groups of 30 female rabbits each were randomized to receive III-TT lot 3-1-96 vaccine, saline-alum, or combinations of these treatments before and after insemination. The dose of conjugated CPS on a weight basis was 1 microg/kg, mimicking the anticipated actual human dose. Based on the weight of the rabbits, this was 20- to 100-fold greater than the expected human dose. Does were pre-assigned to deliver litters naturally or have their kits delivered by Caesarean-section at gestation day 29, to assess late fetal development. Sera from does and kits were collected, and the presence of type III CPS-specific IgG was confirmed by quantitative ELISA. Based on all assessments, GBS type III-TT lot 3-1-96, nor antibody to it did not affect embryo fetal viability, sex ratio, growth or cause malformations (i.e., it was non-teratogenic). In addition, that III-TT lot 3-1-96 was found to be safe and immunogenic in two clinical studies involving healthy non-pregnant adults supports a clinical evaluation of this vaccine in pregnant women.

Evaluation of the developmental toxicity of methyl dihydrojasmonate (MDJ) in rats.

Methyl dihydrojasmonate (MDJ) is a widely used fragrance ingredient. MDJ was evaluated for developmental toxicity in presumed pregnant Sprague-Dawley rats (25/group) at oral dosages of 0, 40, 80 or 120 mg/kg/day in corn oil administered on gestational days 7-20. Dams were observed for viability, clinical signs, body weights, and feed consumption. Caesarean-sectioning and necropsy occurred on gestational day 21. Fetuses were weighed and examined for gender, gross external changes, and soft tissue or skeletal alterations. No maternal or fetal deaths occurred. MDJ-related maternal clinical signs included an increased incidence of sparse hair coat and ungroomed appearance at 120 mg/kg/day. Two dams in this group also had tan areas in the liver and a pale spleen. The 120 mg/kg/day dosage also caused reduced mean maternal body weight gains and body weights during the dosage period and reduced absolute and relative maternal feed consumption for the entire dosage period. No Caesarean-sectioning or litter parameters were affected by dosages of MDJ as high as 120 mg/kg/day, although at the highest dosage a tendency toward slightly reduced, but not statistically significant, fetal mean body weight was observed. No fetal gross external, soft tissue or skeletal changes were attributable to dosages of MDJ as high as 120 mg/kg/day. Based on these data, maternal No-Observable-Adverse-Effect-Level (NOAEL) of 80 and developmental NOAEL of equal to or greater than 120 mg/kg/day were established for MDJ. It is concluded that MDJ is not a developmental toxicant in rats under the conditions of this study.

The perinatal and postnatal toxicity of D-methylphenidate and D,L-methylphenidate in rats.

D-methylphenidate is an enantiomer of D,L-methylphenidate and was developed as an improved treatment for attention deficit hyperactivity disorder (ADHD) in children. The current study was performed to assess the potential perinatal and postnatal toxicity of both compounds in rats. About 125 presumed pregnant rats were assigned to five dose groups of 25 each. They were dosed with 2, 6, and 20 mg/kg/day D-methylphenidate and 40 mg/kg/day D,L-methylphenidate from gestation Day 7 to lactation Day 20. F1 generation rats were rebred to produce F2 fetuses. Various perinatal and postnatal measurements were made for the F0 and F1 rats. Among the significant findings were a reduction in maternal body weight gain for 20 mg/kg/day D-methylphenidate and D,L-methylphenidate and increased incidences of dilated pupil and vocalization for D,L-methylphenidate during the gestation period. Neither compound produced any other significant adverse findings in F0 and F1 generation rats at doses that were at least 25 times the maximum daily human therapeutic dose.

Evaluation of the developmental toxicity of linalool in rats.

The developmental toxicity of linalool, a widely used fragrance ingredient, was evaluated in presumed pregnant Sprague-Dawley rats (25/group). Oral dosages of 0, 250, 500, or 1000 mg/kg/day linalool were administered by gavage on gestational days 7 to 17. The presence of spermatozoa and/or a copulatory plug in situ was designated as gestational day 0. Rats were observed for viability, clinical signs, body weights, and feed consumption. Caesarean sectioning and necropsy occurred on gestational day 21. Uteri were examined for number and distribution of implantations, live and dead fetuses, and early and late resorptions. Numbers of corpora lutea were also recorded. Fetuses were weighed and examined for gender, gross external changes, and soft tissue or skeletal alterations. There were no maternal deaths, clinical signs, or gross lesions that were considered related to linalool. During the dosage period, mean relative feed consumption was significantly reduced by 7% and mean body weight gains were reduced by 11% at 1000 mg/kg/day. During the postdosage period, feed consumption values at 1000 mg/kg/day were significantly higher than vehicle control values, which corresponded to the increase in body weight gains during this period. Caesarean section and litter parameters, as well as fetal alterations, were not affected by linalool at any of the three dosages tested. On the basis of these data, the maternal no observed adverse effect level (NOAEL) of linalool is 500 mg/kg/day, whereas the developmental NOAEL is > or = 1000 mg/kg/day. It is concluded that linalool is not a developmental toxicant in rats at maternal doses of up to 1000 mg/kg/day.

Evaluation of the developmental toxicity of lenalidomide in rabbits.

BACKGROUND: Lenalidomide, a thalidomide analog, is indicated for treatment of patients with deletion-5q myelodysplastic syndromes or multiple myeloma. NZW rabbits were used because of sensitivity to thalidomide's teratogenicity. METHODS: Range-finding and pulse-dosing studies preceded a full developmental toxicity study in New Zealand white (NZW) rabbits (25/group) given lenalidomide (0, 3, 10, or 20 mg/kg/day) or thalidomide (180 mg/kg/day) by stomach tube on gestation days (GD) 7-19. Clinical signs, body weights, and feed consumption were recorded daily from GD 7. On GD 29, standard maternal necropsy, uterine content, and fetal evaluations were carried out. RESULTS: In all studies, thalidomide was selectively toxic to development. In the pulse-dosing study, lenalidomide did not affect development at 100 mg/kg/day. Increases in C(max) and AUC(0-24 hr) values for lenalidomide were slightly less than dose-proportional; lenalidomide occurred in the fetuses. At 10 and 20 mg/kg/day, lenalidomide was maternally toxic (reduced body weight gain and feed consumption; at 20 mg/kg/day, weight loss and one abortion). Developmental toxicity at 10 and 20 mg/kg/day included reduced fetal body weights and increased postimplantation losses and fetal variations (morbidity/purple-discolored skin, undeveloped intermediate lung lobe, irregular nasal-frontal suture, and delayed metacarpal ossification). Thalidomide selectively reduced fetal body weight, increased postimplantation loss and caused characteristic limb and other dysmorphology. CONCLUSIONS: The maternal and developmental NOAELs for lenalidomide are 3 mg/kg/day. Unlike thalidomide, lenalidomide affected embryo-fetal development only at maternally toxic dosages, confirming that structure-activity relationships may not predict maternal or developmental effects. No fetal malformations were attributable to lenalidomide.

Evaluation of the developmental toxicity of alpha-iso-methylionone in rats.

Alpha-iso-methylionone, a widely used fragrance ingredient, was evaluated for developmental toxicity in presumed pregnant Sprague-Dawley rats (25/group). Oral dosages of 0, 3, 10, or 30 mg/kg/day alpha-iso-methylionone in corn oil were administered by gavage on gestational days 7 to 17. The presence of spermatozoa and/or a copulatory plug in situ was designated as gestational day. Rats were observed for viability, clinical signs, body weights, and feed consumption. Caesarean sectioning and necropsy occurred on gestational day 21. Uteri were examined for number and distribution of implantations, live and dead fetuses, and early and late resorptions. Numbers of corpora lutea were also recorded. Fetuses were weighed and examined for gender, gross external changes, and soft tissue or skeletal alterations. No maternal or fetal deaths occurred. No fragrance ingredient-related clinical signs were observed. Feed consumption, body weight gains, gross tissue changes at necropsy, and caesarean section or litter parameters, as well as fetal developmental morphology, were unaffected by dosages of alpha-iso-methylionone as high as 30 mg/kg/day. Based on these data, maternal and developmental no observed adverse effect levels of equal to or greater than 30 mg/kg/day were established for alpha-iso-methylionone. It is concluded that alpha-iso-methylionone is not a developmental toxicant in rats at maternal doses of up to 30 mg/kg/day.

Evaluation of the developmental toxicity of alpha-methyl-3,4-methylene-dioxyhydrocinnamic aldehyde in rats.

The developmental toxicity of alpha-methyl-3,4-methylene-dioxyhydrocinnamic aldehyde (MMDHCA), a widely used fragrance ingredient, was evaluated for developmental toxicity in Sprague-Dawley rats (25/group; cesarean-sectioning identified 21 to 25 pregnant rats/group). Oral dosages of 0 (corn oil), 62, 125, or 250 mg/kg/day were administered by gavage on days 7 through 17 of gestation (GDs 7 through 17). Rats were observed for viability, clinical signs, body weights, and feed consumption. Necropsy and cesarean sectioning occurred on GD 21. Uteri were examined for number and distribution of implantations, live and dead fetuses, and early and late resorptions. Numbers of corpora lutea were also recorded. Fetuses were weighed and examined for gender, gross external changes, and soft tissue or skeletal alterations. Analysis of dosage preparations verified calculated dosages +/-10%. No deaths occurred. Excessive salivation occurred in all groups, but the incidence was increased at 250 mg/kg/day. The 250 mg/kg/day dosage also was associated with a significant increase in the incidences of a clear, red or yellow perioral and/or red perivaginal substance and significant reductions in mean feed consumption and body weight gains (11.6% and 7.4%, respectively) during the entire dosage period. No gross changes attributable to MMDHCA were observed at necropsy. Cesarean section or litter parameters, as well as fetal alterations, were not affected by MMDHCA at 250 mg/kg/day or either of the lower dosages tested. Based on these data, maternal and developmental no-observable-effect levels (NOAELs) of 125 and >250 mg/kg/day, respectively, were established for MMDHCA. It is concluded that MMDHCA is not a developmental toxicant in rats under the conditions of this study and dosing regimen.

Evaluation of the developmental toxicity of acetyl cedrene.

The developmental toxicity of acetyl cedrene (AC), a widely used fragrance ingredient, was evaluated in pregnant Sprague-Dawley rats (25/group). Gavaged dosages of 0 (corn oil), 25, 50, or 100 mg/kg/day were administered on days 7 through 17 of gestation (GDs 7 to 17). First and last day dosing suspensions were analyzed for AC content. All rats were observed daily for viability, clinical signs, abortions, and premature deliveries. Body weights were recorded at frequent intervals. Cesarean-sectioning and necropsy examinations were performed on GD 21. Uteri were examined for number and distribution of implantations, live and dead fetuses, and early and late resorptions. The number of corpora lutea in each ovary was also recorded. Fetuses were weighed and examined for gender and gross external changes and soft tissue or skeletal alterations. Totals of 25, 23, 21, and 24 rats became pregnant in the 0 (control), 25, 50 and 100 mg/kg/day groups, respectively, and analysis of dosage preparations verified that administered dosages reflected calculated dosages +/-10%. No deaths or premature deliveries occurred in the study. Clinical signs included excessive salivation, which was attributed to the administration of AC. When compared to controls, significant reductions in feed consumption and body weight gains occurred only at 100 mg/kg/day. Both absolute (g/day) and relative (g/kg/day) feed consumption values were significantly decreased on GDs 7 to 12. Relative values were decreased significantly on GDs 15 to 18. Body weight gains were significantly reduced on GDs 7 to 10. Mean maternal body weights remained significantly lower than controls on GDs 9 to 14, but a marked compensatory increase in feed consumption on GDs 15 to 18 prevented further deterioration in body weight gains. No cesarean-sectioning or litter parameters were affected by dosages of AC and necropsy of the dams after cesarean section did not reveal any gross changes attributable to AC. No gross external, soft tissue, or skeletal fetal alterations (malformations or variations) were attributed by dosages AC. The average number of ossifications sites per fetus per litter did not differ among the groups. Based on these data, maternal and developmental no-observable-adverse-effect levels (NOAELs) of 50 and 100 mg/kg/day, respectively, were established for AC.

History of the Journal of the American College of Toxicology.

This companion article to the History of the American College of Toxicology also is written in celebration of the 25th Anniversary of the American College of Toxicology (ACT). It relates how the official journal of the College evolved from a privately owned publication, the Journal of Environmental Pathology and Toxicology (JEPT), into publications owned and managed by the College and its Board, for the first 17 years as the Journal of the American College of Toxicology (JACT) and currently as The International Journal of Toxicology (IJT). It relates how the first journal focused on toxicological studies, potential cancer causes and concerns associated with environmental contamination and chemical exposure safety issues. It tells how this journal was replaced by one more broadly based that addressed multiple industries and regulatory approaches, accepted previously unpublishable "no-effect" studies, so important in eliminating unwarranted animal use, and provided review articles, rather than only original research. It also described how the JACT evolved into an international journal finally recognized for its quality reviews and peer-reviewed research. Each of the three journals that represented the College is described, as well as interesting events associated with their development and publication, including the activities and contributions of the first four editors in chief, Drs. Myron A. Mehlman, Mildred S. Christian, Robert M. Diener and Harihara Mehendale.

History of the American College of Toxicology (ACT).

This manuscript is one of two written to celebrate the 25th Anniversary of the American College of Toxicology (ACT). This history of ACT describes its evolution from an entrepreneurial, risk taking model to a conservative business model, fully accepted in the scientific community. ACT started with a small group of scientists who were dissatisfied with the relatively narrow approach to full membership then taken by the Society of Toxicology (SOT). They were excited by new research and collaborative opportunities resulting from an enhanced public awareness of the impact of chemicals on the environment and emerging new methodologies to evaluate human risks of exposure to be chemicals and pharmaceuticals. These toxicologists, many of whom were from industry and government, rather than academia, were tired of being considered socond class citizens and envisioned more open and cross-disciplined approaches. They favored balanced input by academia, industry and government in the overall toxicologic evaluation and risk assessment process. The history of the founding and early development of ACT, as well as the College's growth and eventual acceptance into the scientific community, including its impact on the status quo during the Society's first 25 years, are told by its successive presidents.

A study to develop methodology for feeding 24-hour-old neonatal swine for 3 weeks.

Pediatric evaluations are useful only when the animal model and human neonate have similar timing in system development. The objective of this study was to compare the growth of 24-hour-old swine provided 3 different feeding regimens of a simulated sow milk formula for 3 weeks. Three groups of three swine per sex were used. Group 1 was fed every 4 hours for weeks 1 through 3. Group 2 was fed every 3 hours during week 1 and every 4 hours during weeks 2 and 3. Group 3 (as close to ad libitum as possible) was fed every 2 hours for the first 2 days; every 2.5 hours for the next 2 days; every 3 hours for the next 3 days; and every 4 hours during weeks 2 and 3. No mortality occurred. Body weights were within normal limits. Organ weights, physical and ophthalmologic examinations, hematology and serum chemistry parameters, gross necropsy observations, and microscopic evaluation of the brain, liver, and kidneys were not affected by the three feeding regimens. Day 21 body weight gain of group 3 was greater than that for groups 1 or 2. Mean formula consumption (ounces/day) over 21 days was significantly increased (p < .01) for group 3 (males and combined sexes) compared to the two other groups, supporting the greater weight gain of group 3 versus groups 1 and 2 over the 21-day feeding period. Body weights of the piglets fed simulated sow milk and historical control 21-day-old suckling pigs were within the same range. Only the labor-intensive feeding of simulated sow milk in a regimen close to ad libitum produced maximal weight gain in 24-hour-old piglets during the initial 3 weeks postpartum.

Sexual maturation data for Crl Sprague-Dawley rats: criteria and confounding factors.

BACKGROUND: Considerable concern exists in the scientific community regarding potential effects of endocrine disruptive or modulating environmental agents on male and female reproductive development and capacity. Existing data show that in utero and postnatal exposure of rodents to endocrine modulating chemicals can influence the timing and progression of sexual differentiation and/or maturation (e.g., balanopreputial separation and vaginal opening). METHODS: Sexual maturation data from various types of littering studies using International Gold Standard (IGS) Crl Sprague-Dawley rats were evaluated for consistency with both historical observations and published values from other laboratories. In addition, litters from two developmental neurotoxicology studies were statistically analyzed to identify whether increasing the numbers of pups per litter evaluated affected the interpretation of sexual maturation data sets. RESULTS: Control values for preputial separation and vaginal opening ages ranged from PD 45.0 to 48.0 and from PD 32.0 to 34.0, respectively, regardless of the number of pups evaluated per litter. However, statistically significant delays in sexual maturation were present when three rats/sex/litter were evaluated that were not present when only one randomly selected rat/sex/litter was evaluated. CONCLUSIONS: Standardized procedures and criteria are required to provide consistent intra-laboratory values and reduce inter-laboratory differences in sexual maturation observations. When such criteria are used, these endpoints provide sensitive measures for detecting alterations in sexual maturation. However, our analyses demonstrate that the ability to detect statistically significant and biologically important differences in these endpoints is sometimes impaired by the currently common practice of evaluating only one randomly selected rat/sex/litter. Evaluation of three rats/sex/litter improved the sensitivity of the statistical analysis in detection of treatment-related effects and reduced the probability of identifying a false negative result.

Oral (gavage) two-generation (one litter per generation) reproduction study of pentachlorophenol (penta) in rats.

The potential for pentachlorophenol (penta) to induce general and reproductive/developmental toxicity was evaluated in Crl Sprague-Dawley rats, employing a two-generation reproduction toxicity study. Penta was administered by gavage at doses of 0, 10, 30, and 60 mg/kg/day. In both generations, the parental animals (30/sex/group) were intubated daily for 10 weeks before cohabitation and continuing through cohabitation, gestation, and lactation periods. Intubation of the F1 generation was begun 28 days postpartum. Animals were evaluated daily for mortality and general toxicity (clinical observations, body weights and gains, feed consumption). Organ weights were recorded and histopathological evaluations were made. Specific indices of reproductive function evaluated included estrous cycles, mating and fertility, parturition, lactation, viability, and growth and development of offspring, including sexual maturation, sperm parameters, and numbers of ovarian primordial follicles. All deaths in the parental rats were unrelated to penta. Expected metabolic effects of penta, sporadic increased liver weights associated with hepatocellular centrilobular hypertrophy and vacuolation and lipofuscin pigmentation, were evident in the 10-, 30-, and 60-mg/kg/day dose group P1 and F1 animals. Toxicity, in the form of liver pathology (single cell necrosis), reduced body weights and associated reductions in organ weights, and reduced feed consumption were noted in both generations at the 30- and 60-mg/kg/day doses. Developmental toxicity associated with these doses included reduced pup weights and viability. The 60-mg/kg/day dose also resulted in delayed sexual maturation, decreased spermatid counts, small prostates and testes, decreased implantations, reduced fertility, and increased resorptions of embryos. Based on these results, it was concluded that 30 mg/kg/day is the lowest-observable-adverse-effect level (LOAEL) and 10 mg/kg/day is the no-observable-adverse-effect level (NOAEL) for both reproductive and general toxicity. These findings are consistent with results from previously conducted studies wherein reproductive/developmental toxicity was observed only at doses that also induced general toxicity. It differs from previous findings in that the NOAEL for general toxicity is two to three times higher for the more pure product than for products produced and tested previously. In addition, the results did not indicate bioaccumulation of penta. Thus, penta did not selectively affect reproduction or development of the offspring of rats at a dose of 10 mg/kg/day, a dose that is 7000 to 20,000 times higher than human exposure.

D-methylphenidate and D,L-methylphenidate are not developmental toxicants in rats and rabbits.

BACKGROUND: D,L-threo-Methylphenidate (D,L-MPH) is marketed currently for attention deficit hyperactivity disorder in children. D-threo-methylphenidate (dexmethylphenidate; D-MPH) is a refined formulation of D,L-methylphenidate containing only the active enantiomer and was recently approved in the U.S. for the same condition. D-Methylphenidate has been shown to be efficacious in patients at half the dose of D,L-MPH with a potentially improved therapeutic profile. The developmental toxicity of both compounds was determined and compared in rats and rabbits according to current International Conference on Harmonization (ICH) guidelines. METHODS: Groups of pregnant rats were orally dosed twice daily 6 hr apart from Days 7 to 17 of presumed gestation (DG 7-17) for total daily doses of 2, 6 and 20 mg/kg D-MPH and 40 mg/kg D,L-MPH. Groups of presumed pregnant rabbits were similarly dosed from DG 6 to 18 for total daily doses of 4, 20 and 100 mg/kg D-MPH and 200 mg/kg D,L-MPH. Control groups for both studies were given water vehicle. Comprehensive clinical and developmental measurements were made. Satellite groups of animals were included in the main rat and rabbit studies for toxicokinetic assessment. RESULTS: No drug-related mortality was seen in the F0 rats and rabbits. The number of rats with repetitive pawing, dilated pupil and aggression was significantly greater for the 40 mg/kg D,L-MPH compared to the 20 mg/kg D-MPH dosed rats. Maternal body weight and body weight gain were significantly reduced for both D-MPH and D,L-MPH groups compared to control. Maternal reproductive and litter parameters were unaffected by both drugs. No gross external, soft tissue, or skeletal alterations related to both compounds were seen in the fetuses. In rabbits, head-bobbing and hyperpnea were significantly greater for the 200 mg/kg D,L-MPH compared to 100 mg/kg D-MPH. No other maternal or fetal effects related to both compounds were seen. Exposure to D-MPH (as assessed by AUC) showed no teratogenic effects at exposures of up to 5.6 and 1.7 times for the rat and rabbit respectively compared to children taking the maximum therapeutic dose of 20 mg/day (10 mg twice a day). No teratogenic effects were seen for D,L-MPH in rat and rabbit at exposures of up to 3.7 to 11.7 times that of the maximum therapeutic pediatric dose of 60 mg/ day. CONCLUSIONS: Rats and rabbits dosed with D,L-MPH exhibited significantly greater incidence of maternal clinical observations at twice the dose of D-MPH. Both D-MPH and D,L-MPH were not teratogenic in rats and rabbits at higher exposure levels compared to humans.