Male and female weanling Crl:CD®BR rats, approximately 21 days of age, were received from Charles River Laboratories, Inc., Portage, Michigan. Body weights for males ranged from 37 to 74 grams and for females ranged from 30 to 63 grams. This strain of rat was selected based on extensive experience with this strain and its suitability with respect to longevity, hardiness, sensitivity, and low incidence of spontaneous diseases.

Upon arrival at Haskell Laboratory, all rats were removed from shipping cartons and housed three per cage in stainless steel, wire-mesh cages suspended above cage boards. Male and female rats were placed on separate cage racks. During a quarantine period of approximately three weeks the rats were fed irradiated Purina Rodent Chow #5056 (chunk). Tap water was provided ad libitum.

After assignment to a treatment group, each rat was given a unique six-digit number, and an identification number was tattooed on the tail. Rats were housed three per cage, sexes separate, in stainless steel, wire-mesh cages suspended above cage boards. Generally, the number of rats in each cage was adjusted back to three as soon as practical after an animal was found dead or sacrificed. Hale and female rats were housed on separate cage racks. A system of rotation was employed to relocate cage racks within the animal room each week and to reposition the cages on the rack every two weeks.

Exposure groups were housed by concentration in separate laminar flow animal rooms. Animal rooms were targeted at a temperature of 23+/-2°C and a relative humidity of 55+/-15%. Animal rooms were artificially illuminated (fluorescent light) on a 12-hour light/dark cycle.

Leuteinizing hormone (LH)

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