Perinatal exposure to low levels of the environmental antiandrogen vinclozolin alters sex-differentiated social play and sexual behaviors in the rat

Environmental Health Perspectives, June, 2005 by Nathan K.W. Colbert, Nicole C. Pelletier, Joyce M. Cote, John B. Concannon, Nicole A. Jurdak, Sara B. Minott, Vincent P. Markowski

In this study we examined the effects of exposure to the antiandrogenic fungicide vindozolin (Vz) on the development of two sex-differentiated behaviors that are organized by the perinatal actions of androgens. Pregnant Long-Evans rats were administered a daily oral dose of 0, 1.5, 3, 6, or 12 mg/kg Vz from the 14th day of gestation through postnatal day (PND)3. The social play behavior of juvenile offspring was examined on PND22 and again on PND34 during play sessions with a same-sex littermate. After they reached adulthood, the male offspring were examined with the ex copula penile reflex procedure to assess erectile function. Vz did not produce any gross maternal or neonatal toxicity, nor did it reduce the anogenital distance in male pups. We observed no effects of Vz on play behavior on PND22. However, the 12-mg/kg Vz dose significantly increased play behavior in the male offspring on PND34 compared with controls. The most dramatic increases were seen with the nape contact and pounce behavior components of play. The Vz effect was more pronounced in male than in female offspring. As adults, male offspring showed a significant reduction of erections at all dose levels during the ex copula penile reflex tests. The 12-mg/kg dose was also associated with an increase in seminal emissions. These effects demonstrate that perinatal Vz disrupts the development of androgen-mediated behavioral functions at exposure levels that do not produce obvious structural changes or weight reductions in androgen-sensitive reproductive organs. Key words: antiandrogen, penile reflexes, prenatal exposure, rat, social play, vindozolin. Environ Health Perspect 113:700-707 (2005). doi: 10.1289/ehp.7509 available via http://dx.doi.org/[Online 16 March 2005]

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Fungicides are applied to many foods to control plant diseases such as Sclerotinis sclerotiorum (white mold) and Botrytis cinerea (gray mold) (Papadopoulou-Mourkidou 1991). After application, fungicides have been shown to volatilize and circulate through air and water and on untreated foods, increasing their distribution (Baumeister et al. 2002). Consumers cannot readily reduce their exposure because fungicides are not removed from fresh produce by rinsing with tap water (Krol et al. 2000), and commercial processing increases their concentrations (Will and Kruger 1999). Fungicides are also widely used on golf courses, industrial landscapes, lawn turf, and ornamental plants, where they can enter water supplies in contaminated runoff (Haith and Rossi 2003).

The dicarboximide fungicide vindozolin (Vz) is used in a number of commercial formulations to treat fruits and vegetables such as lettuce, snap beans, canola, and grapes [U.S. Environmental Protection Agency (EPA) 2003]. Vz belongs to a group of environmental endocrine disruptors known as the antiandrogens. These compounds share a common, clearly defined hormone-receptor-mediated mechanism of action. Vz is biotransformed into at least two active metabolites that bind competitively to the human, monkey, and rat androgen receptor (Kelce and Monosson 1995; Kelce et al. 1994). Exposure to antiandrogens during development could have serious effects on sexual development. They are already recognized as one of the factors responsible for the recent increase of hypospadias, a male reproductive disorder where the urethral opening is on the ventral surface of the penis (Baskin et al. 2001; Davis et al. 1998; Egeland et al. 1994; Jensen et al. 1995; Sharpe and Skakkebaek 1993).

To date, most investigations have focused on the impact of the environmental antiandrogens on the development of androgen-sensitive male reproductive organs. For example, adult male rats have reduced anogenital distances (AGDs), reduced seminal vesicle and ventral prostate weights, and lower epididymal sperm counts after perinatal exposure to Vz (Gray et al. 1994; Hellwig et al. 2000). Vz is not the only fungicide that acts as an environmental antiandrogen. Procymidone and iprodione are fungicides that are structurally similar to Vz, and they produce a nearly identical profile of effects on the reproductive system (Gray et al. 1999b; Ostby et al. 1999). All three fungicides have the same final metabolite. However, the doses of Vz that have been shown to affect the weights of reproductive organs in animal studies are quite high, often 5-10 times the U.S.EPA's lowest observed adverse effect level (LOAEL). High doses are associated with measures of gross toxicity such as lowered body weights and increased mortality rate due to granulomas and bladder stones (Gray et al. 1994; Hellwig et al. 2000). Thus, although effects such as reductions in rat reproductive organ weights demonstrate that environmental antiandrogens can produce long-term effects after perinatal exposure, they do not necessarily represent the most sensitive end points. Investigations of the functional effects of low-level environmental antiandrogen exposure are needed to complement the high-dose studies and place organ deficits into the larger context of male reproductive health.