Possible estrogenic and/or antiandrogenic effects of methoxychlor on prolactin release in male rats

Methoxychlor (MTX) is a pesticide currently used as a substitute for dichlo ro-diphenyl-trichloroethane (DDT). This organochloride insecticide has some estrogenic properties, and may modify the feedback mechanisms of steroids on the hypothalamus and pituitary. This work was undertaken to explore the possible effects of MTX on the episodic prolactin release and to analyze wh ether these effects are mediated by dopamine (DA), luteinizing hormone (LH) , and/or testosterone. Adult male Sprague-Dawley rats were administered 25 mg/kg/day of MTX in sesame oil for 30 days. Control animals received vehicl e only. The episodic prolactin release and plasma testosterone levers were measured as well as the dopamine (DA) content in the median eminence (ME) a nd in the anterior (AH), mediobasal (MBH), and posterior (PH) hypothalamus. The mean serum prolactin levers and absolute pulse amplitude of the hormon e increased after the xenobiotic administration, whereas its relative pulse amplitude diminished. The frequency and duration of prolactin peaks and it s half-life were not modified by the treatment with the pesticide. On the o ther hand, methoxychlor decreased the DA content in ME, increased it in AH, and did not change it in MBH or PH. MTX decreased plasma levels of LH and testosterone compared with controls. These data suggest estrogenic and anti androgenic effects of MTX on the episodic prolactin secretion; the changes observed in prolactin release could be explained. at least in part, by some of the changes of DA at the hypothalamus and of LH at the pituitary, but n ot by changes of testosterone at the testicular level.