| Summary: | 博士 === 國立成功大學 === 基礎醫學研究所 === 86 === Lead-induced infertility has been reported in rats and mice. Workers with
elevated blood lead levels were known to have altered spermatogenesis and substantial
decrease of fertile capability compared to unexposed. Although these data are
suggestive of probable toxicity at the hypothalamic-pituitary-testis axis, it is not clear
whether lead directly affects sperm function, and if so, through what mechanisms.
Reactive oxygen species (ROS) are free radicals, such as superoxide anion (O2-.),
hydroxyl radical (OH-.), and hydrogen peroxide (H2O2). Lead-related ROS
formation in the tissue was likely to cause oxidative damage and the oxidative stress
could then contribute to tissue injury in liver, brain and neuron cells, but we don''t
know whether lead enter the cauda epididymis, contact with sperm, and cause ROS
generation. In this study, we found that there was a good dose-related correlation
between the sperm lead levels and lead exposure. Sperm of lead-exposed rats produced
significantly higher levls of ROS, the sperm ROS generation was neggatively
associated with sperm motility and capability of penetration. We suggested that lead
might enter the epididymis and probably affected the sperm function by activating one
of the pathways of ROS generation. Moreover, the antioxidants, vitamin E and C,
were given to the determine whether antioxidants prevents lead related sperm damage.
We found that supplementation with vitamin E and/or C reduced ROS generation and
improved the capability of penetration in lead exposed rats sperm. However, the
intake of vitamin E and/or C did not change the blood and sperm levels of lead in
lead-exposed rats. The result suggested that these ROS-related impairment could be
improved by the administration of vitamin E and/or C.
The capability of sperm-oocyte penetration was one of the important indicators
for sperm function. During sperm transport the female genital tract, mammalian
sperm must undergo a complex process of maturation in order to be capable of
fertilizing the oocyte. This process, called capacitation, culminates in the acrosome
reaction. When or where the acrosome reaction occurs might be an important factors
for fertilizing the oocyte. We found that lead exposure might cause early onset of
capacitation, premature acrosome reaction. These early changes in sperm might be
associated with the decrease of capability for oocyte penetration. According our
research finding, the role of lead-related ROS generation and the possible effects on
sperm function are more clear and offer a new direction to explain the inability of
sperm in lead-related toxicity.
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