Update of OECD DART guidelines with endocrine disruptor relevant endpoints: Practical considerations.

In 1998, the OECD initiated a high-priority project aimed at revising existing test guidelines and developing new test guidelines for screening of potential endocrine disruptors. In 2011, OECD 443 was adopted, and in 2015 OECD 421 and OECD 422 were updated with endocrine disruptor relevant endpoints. A feasibility study for the enhancement of OECD 414 with endocrine disruptor relevant endpoints is currently ongoing. The addition of these endpoints is considered crucial for gaining more information on endocrine disruptor potency of tested chemicals, however it should be noted that these additions have a major impact on the study designs and give rise to several practical challenges. The aim of this review is to discuss important aspects of these challenging study designs and to share our knowledge on their implementation in our laboratory. Together, this review can be used as guidance for other laboratories, study monitors and registration officers.

A Combined 28-Day Oral Toxicity Study of HFPO-Amidol (CASRN 75888-49-2) With Reproductive/Developmental Toxicity Screening Test in Wistar Han Rats.

HFPO-Amidol (CAS # 75888-49-2) is a new hexafluoropropylene oxide (HFPO)-based intermediate developed as an alternative to longer chain perfluorinated compounds. The repeated-dose toxicity of this material was evaluated in an Organization for Economic Cooperation and Development 422-compliant, 28-day oral exposure study with a concurrent reproductive/developmental toxicity screening test. Wistar rats received doses of 0, 30, 300, or 1000 mg/kg/d by oral gavage. Statistically significant changes in body weight gain of 1000 mg/kg/d females during the postcoitum period were possibly related to treatment but were considered not adverse, given the slight nature of the changes. The lower food consumption of 300 mg/kg/d females during the postcoitum and lactation period was not considered treatment related given the absence of a time- and dose-related trend and because food intake was generally similar to control levels after allowance for body weights. Statistically significant changes in motor activity (total movements and total ambulations) were noted in 1000 mg/kg/d main male and female rats. The changes observed in female rats were considered not treatment related in the absence of a dose-response trend. The higher motor activity of high-dose males was primarily apparent within the first 10 minutes of the 60-minute measurement period and was suggestive of temporary hyperreactivity to a new environment/stimulus. This increased peak motor activity remained present although at an apparent lower magnitude when measured 13 days after withdrawal of treatment. Because the possible toxicological relevance of the temporarily increased motor activity observed in 1000 mg/kg/d males could not be excluded, these changes were considered possibly adverse in nature. No treatment-related or toxicologically relevant effects were noted on the other parental, reproductive, and developmental parameters investigated in this study. The parental systemic no observed adverse effect level (NOAEL) for this study is 300 mg/kg/d (based on increased motor activity in males), while the reproductive and developmental NOAEL is 1000 mg/kg/d.

The underestimated value of OECD 421 and 422 repro screening studies: putting it in the right perspective.

To assess the efficacy of reproduction/developmental screening studies (OECD 421 and 422), a retrospective evaluation of 134 studies was performed. The major findings were: (1) for up to half of the studies with developmental and reproductive toxicity, these effects would have been missed in other types of studies, which underscores that reproduction/developmental screening studies should not be waived by default based on negative 28-day and/or prenatal developmental data, (2) the required number of animals as stated in the guidelines, is appropriate for detecting developmental and reproductive toxicity, and (3) adding measurements like anogenital distance, internal sex determination and nipple retention, plus extending the postnatal period would add predictive value. Overall, the current reproduction/developmental screening studies are effective in providing unique data, especially considering the limited number of animals used. Some simple additions would enrich its value in risk assessment even further.

Subchronic and reproductive/developmental (screening level) toxicity of complexation products of iron trichloride and sodium tartrate (FemTA).

A complexation/reaction product, termed FemTA, of sodium tartrate [D(-)- and L(+)-tartaric acid and mesotartaric acid], sodium hydroxide, and iron trichloride may have use as an anticaking agent in salt preparations. FemTA is composed of about 4% sodium tartrate, approximately 10% mesotartaric acid, approximately 7% chloride, approximately 4% iron, approximately 7% sodium, approximately 0.3% sodium oxalate, and approximately 65% water. FemTA was tested in a 90-d oral toxicity study, which included a screening level reproductive/developmental toxicity phase, in Harlan Wistar rats. FemTA was administered by oral gavage at 500, 1000, and 2000 mg/kg body weight/d prior to and during mating, or about 20, 40, or 80 mg of iron/kg body weight/d, such that males received 90/91 d of treatment and females 104 to 109 d. Treatment was associated with inflammatory lesions of the lower GI tract at the mid- and high-dose levels, increased liver and kidney weights, increased serum bile acids and blood urea nitrogen, decreased chloride, and changes to hematological parameters consistent with inflammation. The effects were considered the result of iron overload. There were no effects on reproductive/developmental toxicity parameters. The no-observed-adverse-effect level (NOAEL), based on gastrointestinal tract effects was 500 mg/kg body weight/d. The NOAEL for reproductive/developmental toxicity was 2000 mg/kg body weight/d, the highest dose tested.

Toxicological evaluation of ammonium perfluorobutyrate in rats: twenty-eight-day and ninety-day oral gavage studies.

Sequential 28-day and 90-day oral toxicity studies were performed in male and female rats with ammonium perfluorobutyrate (NH(4)(+)PFBA) at doses up to 150 and 30mg/kg-d, respectively. Ammonium perfluorooctanoate was used as a comparator at a dose of 30mg/kg-d in the 28-day study. Female rats were unaffected by NH(4)(+)PFBA. Effects in males included: increased liver weight, slight to minimal hepatocellular hypertrophy; decreased serum total cholesterol; and reduced serum thyroxin with no change in serum thyrotropin. During recovery, liver weight, histological, and cholesterol effects were resolved. Results of RT-qPCR were consistent with increased transcriptional expression of the xenosensor nuclear receptors PPARα and CAR as well as the thyroid receptor, and decreased expression of Cyp1A1 (Ah receptor-regulated). No observable adverse effect levels (NOAELs) were 6 and >150mg/kg-d for male and female rats in the 28-day study and 6 and >30mg/kg-d in the 90-dat study, respectively.