Demasculinization and feminization of male gonads by atrazine: consistent effects across vertebrate classes

Atrazine is the most commonly detected pesticide contaminant of ground water, surface water, and precipitation. Atrazine is also an endocrine disruptor that, among other effects, alters male reproductive tissues when animals are exposed during development. Here, we apply the nine so-called "Hill criteria" (Strength, Consistency, Specificity, Temporality, Biological Gradient, Plausibility, Coherence, Experiment, and Analogy) for establishing cause-effect relationships to examine the evidence for atrazine as an endocrine disruptor that demasculinizes and feminizes the gonads of male vertebrates. We present experimental evidence that the effects of atrazine on male development are consistent across all vertebrate classes examined and we present a state of the art summary of the mechanisms by which atrazine acts as an endocrine disruptor to produce these effects. Atrazine demasculinizes male gonads producing testicular lesions associated with reduced germ cell numbers in teleost fish, amphibians, reptiles, and mammals, and induces partial and/or complete feminization in fish, amphibians, and reptiles. These effects are strong (statistically significant), consistent across vertebrate classes, and specific. Reductions in androgen levels and the induction of estrogen synthesis - demonstrated in fish, amphibians, reptiles, and mammals - represent plausible and coherent mechanisms that explain these effects. Biological gradients are observed in several of the cited studies, although threshold doses and patterns vary among species. Given that the effects on the male gonads described in all of these experimental studies occurred only after atrazine exposure, temporality is also met here. Thus the case for atrazine as an endocrine disruptor that demasculinizes and feminizes male vertebrates meets all nine of the "Hill criteria".

Cellular and regional distributions of ubiquitin-proteasome and endocytotic pathway components in the epithelium of rat efferent ductules and initial segment of the epididymis

Efferent ductules of the male reproductive tract contain high concentrations of estrogen receptors (ER), which are essential for the regulation of fluid reabsorption and maintenance of normal epithelial morphology. Treatments with the antiestrogen ICI 182,780 and 17beta-estradiol cause a reduction in ERalpha expression; however, the mechanisms governing the down-regulation are undetermined. In other tissues, the ubiquitin-proteasome pathway appears to have a dominant role in regulating ERalpha turnover, although in the efferent ductules, an abundance of epithelial lysosomes could also participate in protein turnover. To study this activity, the expressions of proteasome, ubiquitin, and markers for the endocytotic apparatus (early endosome antigen-1 [EEA1], clusterin, and cathepsin D) were examined in rat efferent ductules and initial segment of epididymis. Distinct cellular, subcellular, and regional distributions of these proteins were observed in the epithelial cells. A gradient of proteasome, ubiquitin, EEA1, and clusterin staining was seen in the efferent ducts, which decreased 30%-41% from the proximal zone to the terminal common duct. Antiestrogen treatment resulted in significant decreases in proteasome, EEA1, and clusterin in the efferent ducts. Localization of ubiquitin-proteasome and endocytotic pathway components suggests that differential regulation is required for protein degradation and turnover in efferent ductules and head of the epididymis.