ON TESTIS AND EPlDlDYMlS OF RATS - Pondicherry University ...

1997). This deficiency is characterized in adult rats by decreased plasma testostcronc
and DHT concentrations, unaltered plasma LH concentrations and unchanged plasn~a
clearance of androgens and LH (Moore er al., 1985; Moore el ul., 1989). The doserelated
reduction in plasma testosterone and DHT concentrations along with the
weights of the seminal vesicles and ventral prostate weights in rats has been reported
(Moore er a/., 1985). In contrast, TCDD did not affect accessory sex organ weights in
castrated adult rats implanted with either testosterone or DHT containing capsules
(Bookstaff er al., 1990). Trophic responsiveness of the seminal vesicles and ventral
prostate to testosterone and DHT has been shown to remain unaffected by
postpubertal TCDD treatment TCDD could increase responsiveness of the pituitary to
these androgens without affecting the responsiveness of the accessory sex organs
(Gray er al., 1997). TCDD has been shown to increase epididyrnal transit rate of
sperm through the cauda epididymis of rat primarily due to decreased transit rate ol'
sperm through the caput and corpus epididymis (Wilker er al., 1996).
1.3.1.3 Mechanism of TCDD action
TCDD has been shown to act through aryl hydrocarbon receptor (AhR).
AhR has been shown to modulate the expression of a number of phase I and phase I1
enzymes responsible for detoxification1 bioactivation of a variety of lipophilic
compounds (Hankinson, 1995). This modulation has been shown to be accomplished
through ligand AhR complex interactions with specific DNA response elements called
dioxin-response elements or xenobiotic-response elements (Safe, 1995). A number of
genes, which are involved in the oxidative metabolism, havc been shown to be
induced by the AhR including CYPIA1, CYPl A2 and CYPl Bl (Spink el 01.. 1990;
Spink ef al., 1994; Safe. 1995; Hankinson. 1995). TCDD has been shown to induce
the production of reactive oxygen species thereby causing oxidative stress in multiple
tissucs through AhR activation or AhR mediated xanthine oxidascl santhinc
dehydrogenase activity (Stohs, 1990: Safe, 2001; Sugihara o 01.. 2001). Thc
mechanism of TCDD mediated reactive oxygen species production has been proposed
to involve cytochrome P450s (Park el ol., 1996;.