Effects of the chlorinated hydrocarbon (dieldrin) on testicular morphology and endocrinology in the male rat
Abstract
Experimental studies portray that a large number of chemicals namely environmental and
industrial pollutants affect the male reproductive system. Reproductive toxicants exert
their effect at different stages of the male reproductive system with some influencing the
central and the autonomic nervous systems and lor the hypothalamic pituitary - testicular
axis causing reproductive dysfunction. This study investigated the biological effects of
parenteral and oral administration of dieldrin on reproductive function of mature male rats.
In another set of experiments the effect of parenteral administration of dieldrin on plasma
testosterone levels and histology of the testicular tissues of neonatal male rats were
investigated.
Dieldrin was injected subcutaneously to mature male rats (Spraque- Dawley) every other
day for 20 days. Experimental rats received dieldrin at a dose of either 5mg (n=10) or
10mg (n=IO) Ikg body weight in corn oil while the control group (n=IO) was treated with
the vehicle (corn oil). All animals were killed at the end of the experiment and blood
samples were assayed for testosterone and luteinizing hormone (LH). Testicular tissues
from one testis of each rat were processed for histological examination and Leydig cells
were isolated from the other testis and incubated with LH to investigate testosterone
production in vitro. Dieldrin depressed plasma testosterone levels at a dose of 10mg/kgbody
weight and depressed plasma LH at both 5 and lOmg/kg-body weight (P<0.05).
Also, dieldrin significantly suppressed the production of testosterone by Leydig cells ill
vitro (P<O.OOI).
In another set of experiments, mature male rats were fed on dieldrin spiked diet ad-libitum
for 20 days. Experimental rats received dieldrin at a dose of either Smg (n=10) or 10mg
(n=10) /kg- body weight while the control group received a dieldrin free diet. All animals
were killed at the end of the experiment and blood samples were assayed for testosterone
and LH while testicular tissues were processed for histological examination. There were
no significant differences (P>O.OS) in plasma testosterone and LH concentrations between
rats fed dieldrin spiked and dieldrin free diets. In the two experiments, the histology of the
testes and epididymis was not altered in dieldrin treated rats.
In another experiment dieldrin was subcuteneously injected to one to two days old male
rats at every other day interval for 10 days. Test animals received dieldrin at a dose of
either Smg (n=12) or 10mg (n=12)/rat in O.lmL of vehicle while the control group (n=12)
received 0.1mL of corn oil. At the end of the experiment all rats were killed and blood
samples were assayed for plasma testosterone and testicular tissues were processed for
histological examination. Dieldrin significantly suppressed testosterone concentration in
plasma in a dose-related manner (P<O.OS). In the treated animals the histology of the
testes and epididymis was not altered.
In the last experiment mature female rats of proven fertility (multipara) were allowed to
mate with male rats treated with either vehicle or dieldrin. The number of pregnant
females and their subsequent litter sizes were recorded. There was no significant
differences (P>O.OS) in the number of pregnant females and the subsequent litter sizes
between females mated to males treated with either corn oil or dieldrin.
In conclusion, these results indicate that dieldrin has less affects on the testosterone and
LH concentrations in plasma when given orally than when given parenterally to mature
rats at either Smg or 10mg/kg-body weight doses. Also in addition, these results indicate
that dieldrin decreases plasma concentration of testosterone in male neonate rats. Lastly, it
was shown that dieldrin when administered at doses Sand 10mg/ bwt has no short-term
effects on the fertility and histology of the testicular tissues of treated rats.
Citation
Master of Science in Reproductive BiologyPublisher
University of Nairobi Department of Animal Physiology, University of Nairobi,