Exposure of neonatal female rats to p-tert-octylphenol disrupts afternoon surges of luteinizing hormone, follicle-stimulating hormone and prolactin secretion, and interferes with sexual receptive behavior in adulthood

The present study investigated the effects of exposure of neonatal female r ats to p-tert-octylphenol (OF) on estrogen-induced afternoon surges of LH, FSH, and prolactin (PRL) secretion, and on sexual behavior in adulthood. Af ter birth, one group of female Wistar rat pups received s.c. injections of OP (100 mg/kg body weight [BW]; OP group) dissolved in DMSO, while the cont rol group received DMSO only (DMSO group). In order to make a qualitative c omparison, a third group was injected with estradiol-17 beta (500 mug/kg BW ; estradiol group) dissolved in DMSO. Injections were given on Days 1, 3, 5 , 7, 9, 11, 13, and 15 of age. The rats from the OP and estradiol groups th at were used for subsequent experiments were in persistent vaginal estrus. Spontaneous LH surge measured at Postnatal Days (PND) 78-81 was observed on ly in the DMSO group on the afternoon of the day of proestrus. At PND 115, randomly selected rats from each of three treatment groups were bilaterally ovariectomized (ovx), and 8 days later, Silastic capsules containing estra diol-17 beta were implanted under the skin. Estrogen implants stimulated af ternoon surges of LH, FSH, and PRL for two consecutive days in the DMSO gro up, but not in the OP and estradiol groups. Rats from the OP and DMSO group s underwent ovx at PND 186, and 6 days later they were treated with a combi nation of estradiol benzoate s.c. (15 mug/kg BW) and progesterone s.c. (2 m g/kg BW) to test the lordosis reflex. In response to this hormone treatment and mounting stimulus delivered by the stud male rats, the OF-treated rats were less receptive compared with control DMSO-treated rats, and thus the lordosis quotient and lordosis rating were significantly (P < 0.05) reduced in the OP group compared with the DMSO group. Analysis of the area of the sexually dimorphic nucleus of the preoptic area of the brain revealed that the area of this nucleus was larger in the OP group than it was in control DMSO rats. We conclude that the exposure of neonatal female rats to higher doses of OP disrupts the cyclic release of LH, FSH, and PRL, and interferes with the display of sexual receptive behavior in adulthood.