BIOLOGY OF REPRODUCTION 61, 1242–1248 (1999)
Androgen and Estrogen Metabolism in the Reproductive Tract and Accessory Sex
Glands of the Domestic Boar (Sus scrofa) 1
James I. Raeside,2 Heather L. Christie, and Richard L. Renaud
Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1
ABSTRACT
Steroid metabolism in target tissues has relevance in assessing biological response. We have investigated the metabolism of
testosterone and estrogens in the reproductive tract and accessory sex glands in the boar. Seminal vesicles were taken from
four 6-mo-old animals; and seminal vesicles, prostate, vas deferens, and regions of the epididymis were taken from two mature boars (10 and 24 mo old). Tissues were incubated in 5 ml
medium (TC-199) at 348C under 5% CO2 and 95% air for 2 h
with 3H-labeled testosterone, estrone, and estradiol-17b. Aliquots of spent media were taken to measure radioactivity before
separation of unconjugated and conjugated steroids on Waters
C18 Sep-Pak cartridges. Sulfoconjugated steroids and glucuronidates were recovered in series from C18 cartridges after solvolysis and enzyme hydrolysis, respectively. Profiles of metabolites
for free and hydrolyzed fractions were obtained from gradient
HPLC with acetonitrile:water on a reversed-phase C18 column.
No clear evidence of conjugation was seen for testosterone metabolites. 5a-Dihydrotestosterone was the principal metabolite,
but the amounts formed depended on the source, with little
from the epididymal tissues and seminal vesicles, but greater
quantities from the vas deferens (. 25%) and prostate (. 30%).
The most noteworthy feature of estrogen metabolism was the
extent of conjugation by all tissues. Almost all radioactivity in
the conjugate fractions for the epididymis and vas was present
as sulfates. Glucuronidates were seen for the prostate and were
the dominant form of conjugation (about 60%) for the seminal
vesicles. A striking parallel existed for the profiles of estrogen
metabolites from all tissues for unconjugated and hydrolyzed
fractions. Only in quantitative terms were some distinctions noted. These overall findings underscore a need to consider local
metabolism of steroid hormones in target tissues of the male
reproductive system.
INTRODUCTION
Metabolism of steroids in target tissues of the reproductive system has received scant attention in comparison to
steroid receptors. Androgen regulation of activity in tissues
of the male reproductive system is known to depend in
large part on the metabolism of testosterone to 5a-dihydrotestosterone [1]. Further metabolism may result in products
that either contribute to additional biological activation or
represent a pathway for reduction in the stimulation by testosterone [2]. This latter objective would include the possibility of formation of water-soluble conjugates, such as
those from glucuronosyltransferase activity with C19 steroids in the human prostate [3, 4]. To this end also, it may
be noted that steroid sulfotransferase activity has been recorded for the reproductive tract of the male hamster [5];
Accepted June 17, 1999.
Received April 21, 1999.
1
This work was supported by a grant from the Natural Sciences and
Engineering Research Council of Canada and by the Ontario Ministry of
Agriculture, Food and Rural Affairs.
2
Correspondence. FAX: 519 767 1450;
e-mail: [email protected]
however, its relevance for testosterone metabolism is in
some doubt since D5-3b-hydroxysteroids are the preferred
substrates. In addition to conjugation, it is likely that metabolism of testosterone to such polar compounds as androstanetriols would give rise to hydrophilic products that
could be removed easily as water-soluble substances and
thus contribute to down-regulation in the response.
A role for estrogens in the male reproductive system has
become the focus of increased attention [6]. Recently, a
specific physiological endpoint of estrogen action in the
male has been demonstrated for the first time, in the stimulation of reabsorption of luminal fluid by the efferent ductules of rat testes [7]. Reports on the presence of the estrogen receptors (ERa and ERb) at many sites in the male
reproductive system [8–10] suggest that estrogens may
have an extensive role in the regulation of reproductive
functions in the male. In this context, our earlier work revealed that estrogens act synergistically with testosterone
on the accessory sex glands and libido in boars castrated
after reaching maturity [11]. It may be noted here that the
boar is remarkable for its high levels of testicular estrogen
secretion [12–14] as well as for its exceedingly large volume of semen (200–500 ml) at ejaculation [15]. Estrogens
also appear to be important along with androgens as regulators of epididymal development and function in the rabbit [16, 17] and rat [18]. Moreover, the early investigations
on the induction of prostatic hypertrophy in the dog [19]
were followed by many studies confirming that estrogens
synergize with 5a-reduced androgens in the dog prostate
gland [2]. Enhanced prostate growth may have resulted
from a synergistic effect of estrogens and androgens leading to an elevation of 5a-reductase activity as seen in the
rat [20].
Estrogen metabolism in the body occurs mainly in the
liver. However, evidence is accumulating that metabolism
of estrogens in target cells may contribute to the overall
response to the hormone [21]. A hypothesis is emerging
that the biological effects of an estrogen will depend on the
profile of multiple metabolites formed and the biological
activities of each of the metabolites. This view was expressed earlier for testosterone [22] and is now well recognized. The aim of the present study was to investigate
the potential for metabolism of testosterone, as well as estrogens, by tissues from several components of the reproductive system in the mature boar.
MATERIALS AND METHODS
Reagents
Radiolabeled [1,2,6,7-3H(N)]testosterone (96.5 Ci/mmol)
was obtained from NEN Life Science Products Inc. (Boston, MA); both [2,4,6,7-3H]estrone (101 Ci/mmol) and
[2,4,6,7-3H]estradiol (83 Ci/mmol) were from Amersham
Canada Ltd. (Oakville, ON, Canada). Nonradioactive steroids were purchased from Steraloids Inc. (Wilton, NH).
Solvents were glass-distilled, reagent-, or HPLC-grade from
1242
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ANDROGEN AND ESTROGEN METABOLISM IN THE BOAR
Caledon Laboratories Ltd. (Georgetown, ON, Canada).
Sep-Pak C18 cartridges were purchased from Waters Scientific (Mississauga, ON, Canada). b-Glucuronidase (Type
B-1, from beef liver) was supplied by Sigma Chemical Co.
(St. Louis, MO). All other chemicals were analytical grade
from Sigma or from Fisher Scientific (Toronto, ON, Canada).
Preparation and Incubation of Tissues
TABLE 1. Distribution of radioactivity as unconjugated and conjugated
metabolites of [3H]testosterone after incubation with tissues from the
boar.a
Experiment 2
Tissue
Epididymidis
Caput
Corpus
Cauda
Vas deferens
Prostate
Seminal vesicle
Unconjugated
92.9
95.2
94.8
91.8
92.1
91.8
Experiment 3
Conjugated
Unconjugated
Conjugated
4.3
1.7
1.9
3.4
4.4
4.4
82.8
89.1
85.8
84.7
90.2
90.2
5.3
3.5
6.7
5.1
3.1
3.1
Seminal vesicles were removed at slaughter from 4 pubertal Yorkshire male pigs (6 mo old) in experiment 1. For
experiments 2 and 3, an adult male animal (10 mo old) and
a mature boar (2 yr old) were used, respectively. In the
latter two experiments, the reproductive tracts and accessory sex glands were recovered at slaughter (experiment 2)
or after intravenous injection of pentobarbital (experiment
3). All tissues were placed on ice and taken to the laboratory for incubation within 2 h. The glands were dissected
free of extraneous tissues and minced finely by hand, or
with a McIlwain tissue chopper (Gomshall, Surrey, UK),
before being divided into equal portions. After the vas deferens was stripped, it was minced and transferred to a test
tube containing physiological saline. Portions of the midregions of the caput, corpus, and caudal epididymides were
dissected out and placed separately in saline after mincing.
Three washes of all tissues from the reproductive tract were
done to remove spermatozoa by suspension and gravity
sedimentation in saline solution.
Tissues were incubated for 2 h in 5 ml of culture medium (TC-199) in 25-ml Erlenmeyer flasks at 348C under
5% CO2 and 95% air in a shaking water bath, with 3Hlabeled steroids (about 2 3 106 cpm, in duplicate or quadruplicate). The amount of tissue dispensed was approximately the same for both glands and various regions of
the tract in each experiment, and was approximately 0.5
g (wet weight) per flask. After incubation, the contents of
the flasks were transferred to tubes for centrifugation to
recover the media. The tissues were washed twice by resuspension and centrifugation in 1 ml of TC-199, and the
washings were pooled with the spent media for storage in
glass vials at 2208C until processed as follows. The
thawed contents of each vial were vortexed, and an aliquot
(1/100th) was taken to measure radioactivity by liquid
scintillation counting (LSC).
Free steroids obtained at this stage (third cartridge) were
designated as the ‘‘glucuronidate’’ fraction; and the nonhydrolysed steroids eluted with methanol were considered
to be ‘‘conjugated’’ in an unknown form(s).
The amount of radioactive material recovered from each
incubation was determined by LSC in a 5-ml cocktail
(Ecolite; ICN, Costa Mesa, CA), by taking an aliquot after
thawing but before solid-phase extraction on Sep-Pak C18
cartridges. Similarly, the dried eluates of subsequent separations on C18 cartridges were dissolved in methanol, and
aliquots were removed for counting radioactivity. This was
done at each stage in a series and served also to ensure that
sufficient radioactive material was taken for a reliable estimation of its distribution at the next step.
Unconjugated and hydrolyzed steroids in the fractions
obtained serially from Sep-Pak cartridges were examined
by HPLC. Profiles for the steroids were generated by a
method developed in our laboratory (unpublished results)
and described briefly in a recent report [23]. A binary solvent gradient of acetonitrile-water was used with a Waters
HPLC (Waters Corp., Milford, MA) at a flow rate of 2 ml/
min, and absorbance was monitored at 254 and 280 nm.
Fractions (1 ml) were collected automatically (LKB RediFrac; Pharmacia, Kalamazoo, MI) into vials, and 5 ml Ecolite cocktail was added for LSC.
Analytical Procedures
RESULTS
Steroids in the media were recovered by solid-phase extraction (Waters C18 Sep-Pak cartridges) as described previously [23]. Unconjugated and conjugated steroids were
eluted from the primed cartridges with 5 ml diethyl ether
and 5 ml methanol, successively. The ether and methanol
eluates were evaporated separately under nitrogen at ,
458C. The conjugated material underwent two hydrolytic
processes, in series; in each case, the recovery of free steroids from Sep-Pak cartridges was as described above.
These steps were briefly as follows: the dried methanol
(conjugate) fraction from the first cartridge was acid-solvolysed overnight at 458C with trifluoroacetic acid:ethyl acetate (1:100; v:v) to obtain a ‘‘sulfate’’ fraction, as free
steroids; and the conjugated material (methanol eluate)
from the second cartridge was submitted to enzyme hydrolysis. The dried methanol fraction was reconstituted in 0.5
ml of 0.5 M sodium acetate buffer (pH 5.0), and 1250 units
of b-glucuronidase (type B-1, from beef liver) were added
in 25 ml of the buffer for incubation at 378C overnight.
Distribution of Testosterone Metabolites
a Mean percentages of total radioactivity recovered in the media, based
on duplicate incubations; losses were usually , 10% and occurred in the
‘‘flow through’’ fraction collected before elution of steroids from the SepPak cartridge.
Most of the radioactivity was recovered in the media
after incubation regardless of the source of the tissue
(mean% 6 SD 5 74.7 6 5.0, n 5 20). The data that follow
relate only to work done on the media samples. Radioactivity was present mainly (88.0% 6 3.2, n 5 4) in the
unconjugated fraction in experiment 1, in which only the
seminal vesicle glands from peripubertal animals were
used. For the older, single boars, the amounts of unconjugated (‘‘free’’) steroids were predominant again from incubations of the seminal vesicles (91.8% and 90.2%) as
well as from all other sources of tissues (ranging from
82.8% to 95.2%, Table 1).
Distribution of Estrogen Metabolites
Metabolism of the estrogens was markedly different
from that of testosterone and was notable for the extent to
which conjugation had occurred (Table 2). Data were ob-
1244
RAESIDE ET AL.
TABLE 2. Distribution of radioactivity as unconjugated and conjugated metabolites of [3H]estrone and [3H]estradiol-17b after incubation with tissues
from the boar.a
Experiment 2
Experiment 3
Unconjugated
Tissue
Epididymidis
Caput
Corpus
Cauda
Vas deferens
Prostate
Seminal vesicles
Conjugated
Unconjugated
Conjugated
E1
E2
E1
E2
E1
E2
E1
E2
42.2
41.4
53.1
34.3
69.2
60.3
30.5
41.7
56.6
22.9
—
—
51.4
50.9
32.9
52.8
16.9
27.3
65.4
53.1
38.0
73.4
—
—
46.0
—
—
28.0
73.4b
43.1b
15.9
—
—
30.6
78.9
46.2
50.5
—
—
62.4
18.7b
51.5b
80.7
—
—
65.5
14.5
50.9
a
Mean percentages of total radioactivity recovered from media, based on duplicate, or quadruplicateb incubations.
Quadruplicate incubations. Ranges in quadruplicate incubations were 40.9–47.6 and 64.9–78.0% in the unconjugated fractions and 47.7–54.5 and
14.7–23.2% in the conjugated fractions for the seminal vesicles and prostate, respectively.
b
tained from the two older animals only. With few exceptions the extent of conjugation was about the same for both
estrogens. The highest percentage of radioactivity recovered in the conjugated fraction was found with incubations
of estradiol in the caput epididymidis (80.7%). Conjugated
material from both estrogens was present in greater quantities for tissues from the reproductive tract as compared to
those from the two accessory sex glands. In fact, the prostate gland seemed least able to form conjugates. Separation
of the conjugated material into its components revealed that
most of the radioactivity was in the sulfate fraction in the
case of tissues from the tract, but not from the glands (Table
3). Much lesser amounts were found either as glucuronidates or in the nonhydrolyzed fractions for all segments of
the tract. In contrast, the glucuronidate fraction was the
major one for the seminal vesicles; and a more even distribution resulted for the smaller quantities of conjugates
formed in incubations with prostatic tissues. No marked
differences were seen between the two estrogens upon comparison of the distribution of radioactivity after incubation
with the various tissues.
Profiles of Unconjugated and Hydrolyzed Steroids on
HPLC
No major peaks were formed from [3H]testosterone by
the tissues of the seminal vesicles from all of the peripubertal animals (data not shown). However, one lesser peak
having the same retention time (25 min) as a reference
standard of [3H]5a-dihydrotestosterone (5a-DHT) was
seen with the seminal vesicles of the 10-mo-old animal
(Fig. 1). Profiles for other tissues from this boar showed
marked variation in the amounts of radioactivity corresponding to 5a-DHT, with low activity in the epididymis
and much higher levels in the vas deferens and prostate
(Fig. 1). In general the patterns differed only in quantitative terms. No profiles were run for the minor amounts of
conjugated material from testosterone metabolism in the
seminal vesicles and in all of the other tissues examined
from the older boars.
A remarkable similarity was seen in the profiles of the
unconjugated metabolites of the estrogens for all tissues. In
each case the substrate was the major peak, and differences
were largely restricted to some variation in the distribution
in quantitative terms. Some examples are presented for
[3H]estrone (Fig. 2), where it is clear that little or no estradiol was formed. The same held true for the sulfate fractions, in which the substrate was dominant in the profiles
and the metabolic differences among the tissue sources
again were mainly quantitative (Fig. 3). The same situation
applied for the glucuronidate fractions. Only the sex glands
produced significant amounts of glucuronidates, but all profiles suggested formation of some estrone glucuronidate
(Fig. 4).
DISCUSSION
The metabolism of [3H]testosterone by tissues from the
reproductive tract and glands of the boar was similar to that
found in most species [1]. 5a-DHT was the principal metabolite, but the relative amounts formed varied markedly
among the tissue sources. Its identification was based on
TABLE 3. Distribution of radioactivity as conjugated metabolites of [3H]estrone and [3H]estradiol-17b in the media after incubation with tissues from
the boar.a
Experiment 2
Sulfate
Tissue
Epididymidis
Caput
Corpus
Cauda
Vas deferens
Prostate
Seminal vesicles
a
Glucuronidate
Experiment 3
Nonhydrolyzed
Sulfate
Glucuronidate
Nonhydrolyzed
E1
E2
E1
E2
E1
E2
E1
E2
E1
E2
E1
E2
83.6
83.4
77.1
82.4
17.8
17.0
88.8
77.9
71.0
84.5
—
—
4.0
5.4
8.6
6.1
21.0
59.8
3.6
10.7
15.3
8.0
—
—
10.3
9.2
13.5
9.5
48.0
7.2
5.9
9.0
8.8
5.8
—
—
89.7
—
87.1
—
—
79.9
39.3
7.7
2.3
—
—
4.3
20.0b
66.7b
2.1
—
—
4.6
14.9
68.1
4.6
—
—
9.4
16.7b
9.9b
5.1
—
—
9.8
27.2
9.1
81.9
45.5b
10.4b
Mean percentages of radioactivity in the conjugated fractions based on duplicate, or quadruplicateb incubations.
Quadruplicate incubations. Ranges in quadruplicate incubations for the seminal vesicles, for example, were as follows; sulfates, 9.1–11.9; glucuronidates, 68.8–75.6; nonhydrolyzed fraction, 8.7–11.6%. Losses have not been tabulated.
b
ANDROGEN AND ESTROGEN METABOLISM IN THE BOAR
1245
FIG. 1. HPLC profiles of unconjugated
steroids from incubations of [3H]testosterone with tissues from the reproductive
tract (a, caput epididymis; b, vas deferens)
and the glands (c, prostate; d, seminal vesicles) from a mature boar. Retention time
for a reference standard of [3H]5a-DHT
was about 25 min. Other steroid reference
standards that were run simultaneously
with each extract sample had retention
times (min) as follows: 19-OH-testosterone
(4.1), 6b-OH-testosterone (4.3), 19-OH-androstenedione (5.7), 6b-OH-androstenedione (6.7), 11-b-OH-testosterone (7.1), 11oxo-testosterone (7.5), 11b-OH-androstenedione (10.0), 11-oxo-androstenedione
(10.7), 19-nortestosterone (14.4), 19-norandrostenedione (17.2), testosterone (17.8),
and androstenedione (21.5). UV detection
was done at 254 nm (dotted lines).
coincident elution with a reference standard on HPLC and
on drastic reduction in the size of the peak when an inhibitor of 5a-reductase was used in studies with tissues from
the accessory sex glands of 6-wk-old males (unpublished
results). The profiles of metabolites were practically identical for the various regions of the epididymis, with only
6–7% occurring as 5a-DHT. This finding was unlike the
distribution of the enzyme in the rat epididymis [24, 25],
where it is regulated differentially with respect to region.
However, if the lower part of the tract in the pig is included,
one sees that regional differences in expression of the enzyme exist, with about 4-fold higher levels of 5a-DHT produced by the vas deferens. Because of the key role of the
epididymis in sperm transport, maturation, and storage, further studies including the use of molecular tools [25] are
needed for a better understanding of the significance of local androgen metabolism in the pig.
The most extensive metabolism of testosterone was noted with tissues from the prostate, where the amount of 5aDHT formed was twice as great as that from the seminal
vesicles. This result was the inverse of that in an earlier
report on incubation of minced tissues from these glands in
mature boars [26]. Direct comparison between the two studies is difficult because we used fresh tissues with no cofactors added, rather than thawed tissues with cofactors in the
media. The formation of other metabolites by the prostate
was also evident in the HPLC profile. At much lower levels
than 5a-DHT, some radioactivity appeared to be present as
5a-androstane-3a,17b-diol, which might be expected from
the earlier report [26]. In other respects the profiles for all
FIG. 2. HPLC profiles of unconjugated
steroids from incubations of [3H]estrone
with tissues from the reproductive tract (a,
caput; b, cauda epididymis) and glands (c,
prostate; d, seminal vesicles) from a mature boar. Reference standards of estradiol17b and estrone had retention times of
about 15 and 20 min, respectively (dotted
lines: UV detection at 280 nm). Note differences in total amounts of cpm, which
are a reflection on the amounts of radioactivity available for chromatography at this
stage (see Table 2).
1246
RAESIDE ET AL.
FIG. 3. HPLC profiles of solvolysed steroids (sulfates) from incubations of
[3H]estrone with tissues from the reproductive tract (a, caput; b, cauda epididymis) and glands (c, prostate; d, seminal
vesicles) of a mature boar. See legend to
Figure 2 (and also see Table 3).
tissues bore a striking resemblance to one another, with all
minor peaks being coincident and differing only slightly in
quantitative terms. How these profiles translate to the overall biological responses to testosterone has yet to be addressed.
Both estrone and estradiol-17b are secreted as sulfoconjugated steroids by the testes of the boar [27, 28] and,
as such, are present in high concentrations in peripheral
blood in early postnatal life as well as in adult males
[29].The most noteworthy feature of estrogen metabolism
was the relatively high level of conjugation. Although no
definitive identification of the conjugate forms has yet
been made, the data reveal strong support for the presence
of both sulfotransferase and glucuronosyltransferase activities. Such enzyme activity involving estrogens has not
FIG. 4. HPLC profile of steroid ‘‘glucuronidates’’ from incubations of [3H]estrone
with tissues from the reproductive tract (a,
caput; b, cauda epididymis) and glands (c,
prostate; d, seminal vesicles) of a mature
boar. See legend to Figure 2 (and also see
Table 3).
been recorded for the reproductive tract and associated
glands in males of any mammalian species to our knowledge [30, 31]. This contrasts with the numerous reports on
glucuronidation of 5a-reduced C19 steroids by the prostate
in several species [32]. Since conjugation of a steroid may
abolish its interaction with its receptor and facilitate its
clearance from the cell, the activity expressed in the boar
could be an important component in the regulation of the
levels of active hormone present in the various target tissues. The secretion of characteristically large amounts of
estrogens by the boar testes [12–14] makes it likely that
conjugating enzymes have a significant role to play in this
species. We have recently reported that even in the young
male pig (6 wk old), the accessory sex glands are active
in conjugating estrogens [33]. On the other hand, an ear-
ANDROGEN AND ESTROGEN METABOLISM IN THE BOAR
lier study with the prostate and seminal vesicles of mature
boars did not show conjugated material when tissues that
had been stored at 2708C were incubated with [3H]estrone
and estradiol [26]. Comparison with our positive findings
using fresh tissues is clearly limited by differences in experimental conditions.
A striking difference is seen in the apparent sulfotransferase activity between the tissues from the reproductive
tract and those of the sex glands. While quantitative comparisons were not made, the caput epididymidis seemed
to be the site of highest estrogen sulfate formation. In
contrast, estrogen glucuronidates were clearly most prominent in the seminal vesicles. The outstanding feature for
the prostate was the extent to which estrogen metabolites
could not be liberated by the hydrolysis steps. No explanation can be offered for the obvious specificity in conjugate formation among the tissues; however, the end result would be a reduction in exposure of all of the tissues
to the biologically active form of the estrogen. In this context, mRNA encoding the estrogen receptor (ERb) has
been detected in the reproductive tract of the adult rat,
from the efferent ductules to the vas deferens and in the
prostate [10]. Similar studies in the pig are warranted, especially in view of the in vivo responses to estrogens recorded in our earlier work [11].
Oxidative metabolism of estrogens takes place mainly in
the liver, but many examples of extrahepatic metabolism
have been reported since the early demonstration of 2-hydroxylation of estradiol by the rat brain [34]. In an extensive review of the subject, no reports on the male reproductive system were cited [21]. Our study shows that estradiol (data not shown) and estrone may undergo oxidative
metabolism. Although the substrates were predominant in
the HPLC profiles, several other peaks were present from
both unconjugated and conjugated fractions. No identification has yet been made, but most peaks were more polar
than that for the substrate, which suggests oxidative metabolism to more hydroxylated forms. Whether any of these
metabolites function as secondary hormones with unique
functions and receptors, or compete for the known estrogen
receptors, remains to be determined. In this regard, it has
been recently proposed that the biological effects of an estrogen will depend on the profile of multiple metabolites
formed and on the biological activities of each of the metabolites [21].
In conclusion, our data demonstrate an extensive metabolism of estrogens and, to a lesser degree, of testosterone
in the reproductive tract and accessory sex glands in the
mature male pig. An outstanding feature of estrogen metabolism was the high level of conjugation expressed in
most tissues. Thus, further attention has been drawn to the
need to consider the functional role of steroid metabolism
in target tissues of the male reproductive system.
ACKNOWLEDGMENTS
We wish to thank Dr. R.M. Friendship and B. Bloomfield, Department
of Population Medicine, University of Guelph, for help in collection of
tissues from the boars.
REFERENCES
1. Mainwaring WIP. The Mechanism of Action of Androgens. New
York: Springer-Verlag; 1977: 23–42.
2. Markham CL, Coffey DS. The male sex accessory tissues: structure,
androgen action and physiology. In: Knobil E, Neill JD (eds.), The
Physiology of Reproduction, 2nd ed. New York: Raven Press Ltd.;
1994: 1453–1456.
1247
3. Belanger A, Hum DW, Beaulieu M, Levesque E, Guillemette C,
Tchernof A, Belanger G, Turgeon D. Characterization and regulation
of UDP-glucuronosyltransferases in steroid target tissues. J Steroid
Biochem Mol Biol 1998; 65:301–310.
4. Guillemette C, Hum DW, Belanger A. Evidence for a role of glucuronyltransferase in the regulation of androgen action in the human
prostatic cell line LNCaP. J Steroid Biochem Mol Biol 1996; 57:225–
231.
5. Bouthillier M, Bleau G, Chapdelaine A, Roberts KD. Distribution of
steroid sulfotransferase in the male hamster reproductive tract. Biol
Reprod 1984; 31:936–941.
6. Sharpe RM. Do males rely on female hormones? Nature 1997; 390:
447–448.
7. Hess RA, Bunick D, Lee K-H, Bahr J, Taylor JA, Korach KS, Lubahn
B. A role for oestrogens in the male reproductive system. Nature
1997; 390:509–512.
8. Hess RA, Gist DH, Bunick D, Lubahn DB, Farrell A, Bahr J, Cooke PS,
Green GL. Estrogen receptor (a and b) expression in the excurrent ducts
of the adult male rat reproductive tract. J Androl 1997; 18:602–611.
9. Fisher J, Millar MR, Majdic G, Saunders PTK, Fraser HM, Sharpe
RM. Immunolocalisation of oestrogen receptor alpha (ERa) within the
testis and excurrent ducts of the rat and marmoset monkey from perinatal life to adulthood. J Endocrinol 1997; 153:485–495.
10. Saunders PTK. Oestrogen receptor beta (ERb). Rev Reprod 1998; 3:
164–171.
11. Joshi HS, Raeside JI. Synergistic effects of testosterone and oestrogens on accessory sex glands and sexual behaviour of the boar. J
Endocrinol 1973; 33:411–423.
12. Velle W. Isolation of oestrone and oestradiol-17b from the urine of
adult boars. Acta Endocrinol 1958; 28:255–261.
13. Raeside JI. Urinary excretion of dehydroepiandrosterone and oestrogens by the boar. Acta Endocrinol 1965; 50:611–620.
14. Claus R, Hoffman B. Oestrogens compared to other steroids of testicular origin in blood plasma of boars. Acta Endocrinol 1980; 94:
404–411.
15. McKenzie FF, Miller JC, Bauguess LC. The reproductive organs and
semen of the boar. Res Bull Mo Agric Exp Sta 1938; No 279.
16. Toney TW, Danzo BJ. Estrogen and androgen regulation of protein
synthesis by the immature rabbit epididymis. Endocrinology 1989;
125:231–242.
17. Toney TW, Danzo BJ. Androgen and estrogen effects on protein synthesis by the adult rabbit epididymis. Endocrinology 1989; 125:243–
249.
18. Dhar JD, Mishra R, Setty BS. Estrogen, androgen and antiestrogen
responses in the accessory organs of male rats during different phases
of life. Endocr Res 1998; 24:159–169.
19. Walsh PC, Wilson JD. The induction of prostatic hypertrophy in the
dog with androstanediol. J Clin Invest 1976; 57:1093–1097.
20. Suzuki K, Takazawa Y, Suzuki T, Honma S, Yamanaka H. Synergistic
effects of estrogen with androgen on the prostate—effects of estrogen
on the prostate of androgen-administered rats and 5-alpha-reductase
activity. Prostate 1994; 25:169–176.
21. Zhu BT, Conney AH. Functional role of estrogen metabolism in target
cells: review and perspectives. Carcinogenesis 1998; 19:1–27.
22. Baulieu EE, Laznitzki I, Robel P. Metabolism of testosterone and actions of metabolites on prostate glands grown in organ culture. Nature
1968; 219:1155–1156.
23. Raeside JI, Renaud RL, Christie HL. Postnatal decline in gonadal
secretion of dehydroepiandrosterone and 3b-hydroxyandrosta-5,7dien-17-one in the newborn foal. J Endocrinol 1997; 155:277–282.
24. Viger RS, Robaire B. Immunocytochemical localization of 4-ene steroid 5-alpha-reductase type 1 along the rat epididymis during postnatal
development. Endocrinology 1994; 134:2298–2306.
25. Robaire B, Viger RS. Regulation of epididymal epithelial cell functions. Biol Reprod 1995; 52:226–236.
26. Booth WD. In-vitro metabolism of unconjugated androgens, oestrogens and the sulphate conjugates of androgens and oestrone by accessory sex organs of the mature domestic boar. J Endocrinol 1983;
96:457–464.
27. Raeside JI. Secretion of steroid sulfates by the testes of the boar. Proc
Can Fed Biol Soc 1966; 9:52.
28. Setchell BP, Laurie MS, Flint APF. Transport of free and conjugated
steroids from the boar testes in lymph, venous blood and rete testis
fluid. J Endocrinol 1983; 96:277–282.
29. Schwartzenberger F, Toole GS, Christie HL, Raeside JI. Plasma levels
of several androgens and estrogens from birth to puberty in male domestic pigs. Eur J Endocrinol 1993; 128:173–177.
1248
RAESIDE ET AL.
30. Hobkirk R. Steroid sulfation: current concepts. Trends Endocrinol Metab 1993; 4:69–74.
31. Strott CA. Steroid sulfotransferases. Endocr Rev 1996; 17:670–697.
32. Guillemette C, Hum DW, Belanger A. Levels of plasma C19 steroids
and 5 alpha-reduced C19 steroid glucuronides in primates, rodents and
domestic animals. Am J Physiol 1996; 271:E348-E353.
33. Raeside JI, Christie HL, Renaud RL. Differences in the metabolism
of oestrone, oestradiol-17b and their sulpho-conjugated forms by the
accessory sex glands of the male pig. J Reprod Fertil Abstr Ser 1998;
21:26–27.
34. Fishman J, Norton B. Catechol estrogen formation in the central nervous system of the rat. Endocrinology 1975; 96:1054–1059.