National Toxicology Program

Purpose:

The goal of this is to provide a basis for identifying potential target organs and toxicities and to assist in setting doses for the 13-week exposure study.

1. Treatment:

   After a 10- to 14-day quarantine period, animals are assigned at random to treatment groups. The study includes five treatment groups each administered a different concentration of test article per sex per species plus a control groups. Each group per sex per species contains five animals. The animals receive the test article through a designated route of exposure and the control animals receive vehicle alone. For dosed-feed and dosed-water studies animals are exposed for 14 consecutive days. For inhalation, gavage and dermal studies animals are exposed for 12 treatment days, not including weekends or holidays with at least two consecutive treatment days before the terminal sacrifice day. Male mice are housed individually and rats and female mice are housed in groups of five animals per cage except for inhalation and dermal exposure studies in which all rats and mice are housed individually.

   	Animals		Sexes		Species		Test Groups		Total
   Treatment	5	x	2	x	2	x	5	=	100
   Controls	5	x	2	x	2	x	1	=	20
   ___
   Total									120

2. Observations:

   Animals are weighed individually on day one on test, after seven days, and at sacrifice. The animals are observed twice daily, at least six hours apart (before 10:00 AM and after 2:00 PM) including holidays and weekends, for moribundity and death. Animals found moribund or showing clinical signs of pain or distress are humanely euthanized. Observations are made twice daily for clinical signs of pharmacologic and toxicologic effects of the chemical. For dosed-feed or dosed-water studies, food consumption/water consumption shall be measured and recorded weekly.

3. Necropsy and Histopathologic Evaluation:

   Liver, thymus, right kidney, right testicle, heart, and lung weights are recorded for all animals surviving until the end of the study.

   A complete necropsy is performed on all treated and control animals that either die or are sacrificed and all tissues are saved in formalin. (necropsy list)

   Histopathologic evaluation is done only on those organs/tissues showing gross evidence of treatment-related lesions to a no-effect level plus corresponding tissues are evaluated in control animals. If specific targets are required they shall be read in the control and highest treatment group and the remaining groups to a no-effect level.