Toxicological evaluation of brominated vegetable oil in Sprague Dawley rats

Brominated vegetable oil (BVO) has been approved by the US Food and Drug Administration on an interim basis as a food additive. Past studies have raised concerns about potential toxicities from consuming BVO. To investigate further these toxicities, we conducted a 90-day dietary exposure study in Sprague Dawley rats and analyzed tissue distribution of the main metabolites. Six-week-old male and female rats were fed diets containing 0 (control), 0.002%, 0.02%, 0.1%, or 0.5% BVO by weight. Statistically significant increases were observed in the serum bromide in the high-dose group of both sexes and in the incidence of thyroid follicular cell hypertrophy in the two highest dose groups of males and the high-dose group of females. An increase in serum TSH was observed in the high-dose group for both sexes, as well as a decrease in serum T4 in the high-dose males. A clear dose-response was observed in di- and tetra-bromostearic acid levels in the heart, liver, and inguinal fat. These data expand upon previous observations in rats and pigs that oral exposure to BVO is associated with increased tissue levels of inorganic and organic bromine, and that the thyroid is a potential target organ of toxicity.

Diabetogenic response to streptozotocin varies among obese yellow and among lean agouti (BALB/c x VY)F1 hybrid mice

To test the hypothesis that the elevated insulin levels in obese neoplasia-susceptible yellow Avy/- mice might be a major factor stimulating tumor formation, it is necessary to use normoinsulinemic yellow mice. Although our attempt to obtain normoinsulinemic, euglycemic mice by streptozotocin treatment was unsuccessful, we did observe significant differences in the responsiveness to this treatment among mice of identical genotype. These differences were observed among female yellow Avy/A and agouti A/a (BALB/c x VY)F1 hybrid mice in the responses of body weight gain, plasma glucose, and plasma insulin levels to a single intraperitoneal injection of either 150 or 200 mg/kg streptozotocin (STZ) at 4 weeks of age followed by a 22-week observation period. Among animals treated with the high streptozotocin dose, 80% of the yellow mice gained almost no weight and became grossly hyperglycemic and hypoinsulinemic; however, only 55% of the agouti mice exhibited such a strong response. In the low dose group, 25% of the yellow mice responded with reduced body weight gain, decreased insulin, and elevated glucose levels whereas none of the agouti mice exhibited such responses. More pancreatic islet tissue mass was present in the untreated yellow control mice than among the comparable agouti mice by the end of the study. In both streptozotocin dose groups and in both genotypes, islet tissue mass was reduced to a much greater extent in the more responsive mice than in the less responsive mice. There appeared to be no correlation between islet tissue mass and insulin level. The phenotypic variation in responsiveness to an exogenous agent among test animals of a single inbred or F1 hybrid genotype reported here is not unique to this F1 hybrid since it is seen in most chronic bioassays when relatively low levels of agent are used.

Multistrain experiments for screening toxic substances

The advantages of using homogeneous experimental groups (inbred animal strains) and of using multiple groups within an experiment, based on the power of the Mantel-Haenszel test, were investigated. A simulation experiment was performed to empirically calculate the power of a one-sided Mantel-Haenszel test for multistrain experiments. In each case, the power of the multistrain experiment was compared to the (empirical) expected value, over strains, of the power where each strain is tested individually. In the simulation, use of subgroups, each having different response rates, resulted in an increase in power where a chemical exposure caused an average increase of effects in 10% or more of the animals across strains.

Collaborative Behavioral Teratology Study: statistical approach

The design of the Collaborative Behavioral Teratology Study included six laboratories and two test compounds, d-amphetamine sulfate and methylmercuric chloride. For each lab-compound combination, there were four doses, four replicates (reps), four litters within each dose-rep combination, and eight pups per litter (four males and four females). Two males and two females per litter had early experience testing, the other pups in each litter were naive until day 21 of age. A repeated measures analysis of variance was used to analyze the data. The three major questions addressed were reliability, sensitivity, and effects of early testing experience. The question of litter or pup being the appropriate experimental unit also is discussed. An explanation of interactions and an example of sample size calculations are included.