Reproductive function

Amphibians. Amphibians are highly susceptible to endocrine disruption during development of the larval form and during metamorphosis. The action of metamorphosis is triggered and controlled by the thyroid gland via an increase in triiodothyronine and a decrease in thyroxine, and differs greatly between oviparous and viviparous species. Experimentally, it has been shown that disruption during this sensitive period can lead to malformations and adverse impacts on immune and reproductive functions. 

However, not all EDs with a high log possess or require the ability to bioaccnmulate in order to be biologically active. For example, phthalate plasticisers, chlorophenols from Kraft mill effluents and natural or synthetic hormones can influence an organism s hormone profile and affect reproductive function and immune response without exhibiting bioaccnmiilation. ... 

Breast Cancer. Many studies have observed low incidences of hormone-dependent cancers, particularly breast cancer, in Asian countries compared with Western countries and it is becoming increasingly accepted that dietary factors play an important role. Although breast cancer can occur in either males or females, only about 1 % of all cases occur in men, and male breast cancer is a rare disease in all parts of the world." Although there appear to be some similar risk factors for breast cancer in males and females, there is no indication in the literature that diet is either a risk or a protective factor for male breast cancer. The development of breast cancer is known to be highly dependent on the hormones associated with female reproductive functions, while established genetic factors have been... 

Compounds Affecting Rq>roduction Compounds that can affect reproductive function include several drugs and occupationally important chemicals such as solvents and pesticides as well as a number of environmentally relevant com-fxrunds. A group of chemical compounds that has received much attention recently is endocrine disrupters, many of which are halogenated hydrocarbons, e.g., PCBs. These are known to induce feminization in fish and other animal species.1.5/ There is intense debate about the significance of these compounds to human health. Tobacco smoke and ethyl alcohol also have major effects on human reproduction, the effects of alcohol being especially important. Table 5.17 lists compounds that may disturb the functions of female and male reproductive functions. 

The cytokine leptin is secreted by adipocytes (fat cells) in proportion to the size of the adipose dq>ot and circulates via the bloodstream to the brain, where it ultimately affects feeding behavior, endocrine systems including reproductive function and, at least in rodents, energy expenditure. The major effect of Lqrtin is on the hy-pothalamous, where it suppresses appetite and hence food intake. Leptin exerts its effects via binding to the leptin receptor in the brain (specifically in the hypothalamus), which activates the JAK-STAT Pathway. 

Studies on the reproductive function (three generations) and intrauterine development of rat showed no impairment of the rate of fertility and no sign of any teratogenic effect. The Ames test on mutagenicity was negative [101]. 

No studies were located that examined reproductive function in animals after inhalation exposure to endosulfan. However, routine gross and histopathological examination of the reproductive organs (testes, epididymides, seminal vesicles, prostate, ovaries, and uterus) of rats exposed (nose-only) to concentrations of endosulfan of up to 2 mg/m for 6 hours/day, 5 days/week for a total of 21 out of 29 days revealed no adverse effects (Hoechst 1984c). 

Behavioral effects were noted when reproductive function was assessed in male Long-Evans rats that were given trichloroethylene in com oil by gavage for 6 weeks (Zenick et al. 1984). Copulatory behavior was decreased at 1,000 ppm, and the study authors attributed this to the narcotic properties of trichloroethylene. Sperm count, motility, or morphology were not affected in these rats. The time between dosing and observation of copulatory behavior was not stated. 

Manson JM, Murphy M, Richdale N, et al. 1984. Effect of oral exposure to trichloroethylene on female reproductive function. Toxicology 32 229-242. 

Zenick H, Blackburn K, Hope E, et al. 1984. Effects of trichloroethylene exposure on male reproductive function in rats. Toxicology 31 237-250. 

Perret M. (1995). Chemocommunication in reproductive function of Mouse Lemurs. In Creatures of the Dark The Nocturnal Prosimians (Altermann L., Doyle G. and Izard M., eds.). Plenum, New York, pp. 377-392. 

Prolactin is an essential hormone for normal production of breast milk following childbirth. It also plays a pivotal role in a variety of reproductive functions. Prolactin is regulated primarily by the hypothalamus-pituitary axis and secreted solely by the lactotroph cells of the anterior pituitary gland. Under normal conditions, secretion of prolactin is predominantly under inhibitory control by dopamine and acts on the D2 receptors located on the lactotroph cells. Increase of hypothalamic thyrotropin-releasing hormone (TRH) in primary hypothyroidism can stimulate the release of prolactin. 

A neurotoxic isomer of tricresyl phosphate (tri-ort/20-cresyl phosphate) altered testicular morphology and function as well as reproductive function after oral exposure in rats (Somkuti et al. 1987a, 1987b) (see Section 2.5). 

An organophosphate ester commonly used in hydraulic fluids, tricresyl phosphate (TCP), and tri-ortho-cresyl phosphate (TOCP), a possible contaminant of older formulations of TCP, have been shown to alter testicular morphology, testicular function, and reproductive function in rodents after oral exposure (Carlton et al. 1987 Chapin et al. 1988 NTP 1994 Somkuti et al. 1987a, 1987b). 

R8. Rivier, C., and Vale W., Influence of corticotropin-releasing factor on reproductive function in the rat. Endocrinology 114,914-921 (1984). 

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