Part 1: Male Reproductive Toxicity
Intoduction:
This chapter will review the established toxic responses of the human male and female reproductive systems and of human fetal development. The focus will be on potential human health effects from occupational and/or environmental exposure and examples will be drawn from this area. However, there is much additional mechanistic information from experimental systems and many more chemicalsfor which there are experimental indications of potential reproductive toxicity. In evaluating the importance of such chemicals or mechanisms with regard to human exposure, two basic tenets oftoxicology must be considered: 1) what are the characteristics of a likely exposure, and 2) what could be a relevant dose. Understanding how reproductive processes respond to chemical challenges is the key to addressing these issues.
Topics to be covered include
• Male reproduction and the susceptibility of rapidly dividing germ cells
• Female reproduction and the regulation of endocrine status as a potential target for toxic
responses
• Fetal development—the major opportunities for toxic responses during development and
the established causes of developmental defects
• Current research concerns—hot, timely topics
Objectives:
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To identify toxicants that affect male and female reproductive systems,
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Determine the characteristics and the dose of these toxicants that may cause adverse effect on male and female reproductive systems,
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Explain why reproductive processes respond to chemical challenges is the key to addressing these issues.
(y) Do you know that human diet may contain large amounts of phytoestrogens such as lignans and isoflavones.
Estrogen-blocking effects have been demonstrated in women who ate isoflavones rich diet.
However, most phytoestrogens are metabolized and excreted in urine in the same way as endogenous estrogens and therefore do not accumulate in the body.
The opposite holds true, however, for some other xenoestrogens, including polychlorinated biphenyl (PCBs), dioxins, and furans. Exposure to some PCBs congeners has been correlated with reduced serum motility and density. Furthermore, after in utero exposure, increased fetal loss, reduced birth weight, and behavioral and developmental effects were reported after sever poisoning accidents in Japan and Taiwan.
Occupational exposure to estrogenic compounds like Kepone has also resulted in decreased sperm count and motility and abnormal sperm morphology.
Other xenoestrogens to which human can be exposed are alkylphenols, phthalate, esters, and biphenyl-A.
Considerable concern about these compounds have been raised because they are so pervasive in the environment. In particular, intake of phthalates, which may amount to several hundreds of µg/kg/day, mainly by consumption of food, may result in estrogenic effect.
The most obvious exposure to xenoestrogens is, of course, the direct administration of synthetic hormones, such as diethystibesterol (DES), the effect of which is well documented in women who took it. In some countries, the same hormones may be present in meat and dairy products.
DDT is xenoestrogen and is used as a pesticide.
Now think about some foods that have liganin and isflavones?
What are DDT, Kepone, phthalate, and biphenyl-A?
DDT is insecticide