Vol 43 # 3 September 2011 - Kma.org.kw

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Characterization of Acrylamide Mediated Testicular Toxicity in Rat: Light and Electron ...
September 2011
studies that reported a significant decrease in testis
weight following AA treatment. These decreases were
most likely due to severe atrophy of the testes [6, 8, 25] .
The findings of this study as regards the epididymal
sperm count and morphology tend to support results
reported in a previous study by Yang et al [6,7] . The
results of the current study were also consistent with
the observations made by Sakamoto and Hashimoto [25]
conducted on male mice, which showed a significant
reduction in sperm count and an increase in abnormal
sperm morphology following the administration
of the highest dose of AA (1.2 mM) in the drinking
water. The results of present study are in agreement
with these previous findings of Yang et al [7] . Although
the percentage of abnormal sperm was not calculated
in the current study, it was observed that all of the
AA treated groups showed an abnormal sperm
morphology, characterized by (i) detached heads, (ii)
coiled and fragile tails and (iii) cleaved tails. The most
striking AA induced morphological change was the
appearance of intersegmented tails, a response to AA
that has not been previously reported to the best of our
knowledge, and requires further substantiation and
investigation.
The histopathological findings of this study
were similar to the reports of other investigators [6,
7]
in rat studies and [8] in a mouse study. Hashimoto
et al reported a normal histological appearance of
the epididymis (although there was slight reduction
in relative weights of the epididymis) following AA
treatment of male mice at 1.5 mmol/kg (106.6 mg/
kg, twice weekly by oral gavage for 8 - 10 weeks) [8] .
An attempt has been made by Rotter et al [26] to
explain the mechanism underlying the appearance
of MNG cells in the lumen of the seminiferous
tubules of treated mice. They postulated that
primary 4N spermatocytes were unable to undergo
meiotic division to generate haploid sperm cells and
instead underwent DNA replication only, giving
rise to MNG cells.
The consequence of Sertoli cell injury, which has
been detected as Sertoli cell vacuolations in this study,
is evident in the form of sloughing and shedding of
germinal epithelium, leading to the appearance of
aggregates of cellular material in the lumen [27] . Most
Sertoli cell toxicants alter germ cell attachment to the
Sertoli cell, resulting in loss of germ cell attachment to
the seminiferous epithelium and hence, the presence of
germ cells in the lumen.
The results of the pilot EM study were highly
consistent with the detected histopathological changes
observed by light microscopy. All changes, including
some that had not been detected previously, were
consistent with acute cell injury. Excessive lipid
droplets in the Sertoli cell cytoplasm are indicative of
germ cell degeneration [28] .
One of the atypical forms of the principal
piece detected in control sperm appeared to be an
intersegmented tail when viewed with EM. There was a
partial or complete dissolution of the circumferential ribs
of the fibrous sheath, which probably, led to the inability
of Wright or Rose Bengal stains to colorize the internal
structure of the axoneme. This gave the appearance
of an intersegmented tail under light microscopy.
This abnormality was detected in this study to some
extent in control rats; however, its frequency increased
with AA treatment. Possibly, the genotoxic effect of
AA is exerted mainly on stages of late spermatid and
early spermatozoa formation [17] and hence results in
abnormal sperm morphology. Several mechanisms of
toxicity were proposed and one of these is mediated by
an AA metabolite (glycidamide) as it induces significant
levels of DNA damage as per Hansen et al [29] who have
shown that human lymphocytes are more susceptible to
glycidamide-induced lesions than mouse cells.
Although the histological examination of testis by
light microscopy hinted at Leydig cell toxicity, with the
aid of EM, Leydig cell atrophy was clearly detected.
Furthermore, the signs of insult to Sertoli cells after AA
treatment were signs of Sertoli cell death. This might
be due to a direct influence of AA on Sertoli cells or
may be due to testosterone reduction resulting from
Leydig cell atrophy, or both.
Abnormal spermatogenesis due to a reduction
in testosterone hormone resulting from Leydig cell
atrophy might be another factor for these abnormal
sperms. Another consequence of testosterone reduction
would be abnormal Sertoli cells, because testosterone
influences the Sertoli cell to undergo normal
spermatogenesis [30] . Consequently, this abnormality in
Sertoli cell structure and function results in abnormal
spermatogenesis, while impairment of intercellular
junctions leads to sloughing of germ cells and the
formation of large vacuoles that occupy the basal and
adluminal compartments. In severe cases, Sertoli cells
might be released from epithelium after death, leaving
large basal vacuoles.
Regarding the effect of AA on the widening of
intercellular spaces, Cheville [31] reported dissociations
of desmosomes-like structures (present normally
between cells), and of hemidesmosomes (present
between the cells and the basement membrane), with
subsequent detachment of cells from the basement
membrane and widening of intercellular spaces,
usually signs of acute cell injury. Widening of spaces
surrounding the seminiferous tubules in histological
examinations were believed to be due to Leydig cell
atrophy, and with the aid of EM, Leydig cell atrophy
was clearly detected. This pilot EM study of the AA
treated group (45 mg/kg for five days) needs to be
replicated and validated with additional studies using
larger numbers of exposed and control rats.