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Early
and late long-term effects of vasectomy on Zn, Cd, and Cu levels in prostatic
fluid and serum
Zeng-Nan
MO1, Wei-Hua HUANG1, Jian CHEN1, Xun
HUANG2, Shi-Chun ZHANG3
1Department
of Urology, First Affiliated Hospital of Guangxi Medical University, Nanning
530027, China
2Department of Urology, Second Affiliated Hospital, 3Department
of Urology, First Affiliated Hospital of Hunan Medical University, Changsha
410011, China
Asian J Androl 2000 Jun; 2: 121-124
Keywords:
vasectomy;
serum; prostate; zinc; cadmium; copper; trace elements; sterilization
Abstract
Aim: To evaluate the early and late long-term effects of vasectomy on the serum and prostatic fluid trace elements. Methods: In 37 vasectomized and 25 non-vasectomized (control) men, the Zn, Cd and Cu levels in the serum and prostatic fluid were measured by means of inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Results: No significant difference was found in the prostatic Zn, Cd and Cu levels between the vasectomized and control group. The Zn level in the serum were significantly lower in the vasectomized men than in the controls (11.04 and 13.54 umol/L, respectively; P<0.05), while the serum Cd and Cu levels were not significantly different between the two groups. Conclusion: Vasectomy may decrease the serum, but not the prostatic Zn levels. Its pathophysiological significance is worthy of further investigation.1 Introduction
Evidences
from animal experiments and clinical studies have shown that vasectomy
could inhibit the secretory function of prostate, manifested mainly in
the reduction of secretory products, such as Zn, Mg and critic acid[1-5].
The effect of vasectomy on Zn level merits special attention because of
its close relationship to the maintenance of prostate function, and more
importantly, a possible association between low Zn level and prostate
cancer[6,7]. So far regarding the relationship between vasectomy
and prostatic Zn, mainly the seminal plasma Zn levels have been observed
after relatively short post-vasectomy duration[4,5].
2 Materials and methods
2.1
Subjects
Thirty-seven
vasectomized men and 25 non-vasectomized controls, whose prostatic fluid
was obtained by a routine maneuver, were selected from the subjects in
the previous study[10]. The mean age of subjects in the two
groups was similar. The vasectomized men were divided into two subgroups
according to the years post-vasectomy: VY1 (n=14) consisted of
men having 20 years post-vasectomy
period, and VY2 (n=23), <20 years; their mean ages were
62.7 and 51.2 years, respectively.
2.2
Sample collection
Venous
blood was aspired in the morning and serum was prepared as described elsewhere[10].
After venepuncture, the prostatic fluid was obtained through standard
rectal massage procedure. Subjects were asked to abstain from sexual intercourse
for 3 days preceding the procedure. A qualified urologist was asked to
do the rectal massage in all subjects. Both the serum and prostatic fluid
samples were stored at -20 until assay.
2.3
Trace element determination
Zn,
Cd and Cu were measured by inductively coupled plasma-atomic emission
spectroscopy (ICP-AES) with a BAIRD ICP 2000 Emission Spectrometer (USA)
at sensitivities of 1.5, 2 and 110-12, respectively.
All samples were found to have element concentrations greater than 4 times
their detection limits. Coefficients of variation (CV) for Zn, Cd and
Cu were 1.392%, 1.390%, and 1.420%, respectively.
2.4
Statistical Analysis
Non-parametric
methods were performed due to abnormal distribution of the data. The van
der Warden test was used for the comparison of differences between the
two groups. The Spearman rank sum test was applied to investigate the
relationship between the trace elements. All calculations were performed
on a microcomputer with SAS software. The data were shown in geometric
means and 95% confidence interval (CI).
3
Results
3.1
Trace elements in prostatic fluid
No
significant differences were found in all the elements between the vasectomized
and control groups (Talbe 1).
Table
1. Zn, Cd and Cu levels (geometric mean, mol/L) in prostatic fluid.
|
|
Age |
Zn |
Cd |
Cu |
|
Vasectomized |
58.57.7 |
5055.9 |
1.16 |
6.13 |
|
VY1
subgroup |
51.24.5 |
5633.8 |
1.15 |
6.09 |
|
VY2
subgroup |
62.75.7 |
4733.7 |
1.16 |
6.16 |
|
Non-vasectomized |
57.46.8 |
4641.9 |
1.30 |
6.55 |
The
Zn level in the prostatic fluid was slightly higher in the VY1 than in
the control group, while there was a close approximation between the Zn
level in the VY2 and the control groups. Because of the relatively small
number of the subgroups, significance tests were not performed.
3.2
Trace elements in serum
Results
are shown in Table 2. The Zn level was significantly lower in the vasectomized
men than in the controls (P<0.05). The reduction in Zn following
vasectomy appeared to be more pronounced in the VY1 than VY2 subgroups.
Table
2. Zn, Cd and Cu (geometric mean, mol/L) levels in serum. bP<0.05
compared with non-vasectomized. *P<0.05, vs non-vasectomized.
|
|
Age |
Zn |
Cd |
Cu |
|
Vasectomized |
58.57.7 |
11.4* |
1.03 |
18.35 |
|
VY1
subgroup |
51.24.5 |
10.16 |
1.06 |
17.62 |
|
VY2
subgroup |
62.75.7 |
11.61 |
1.01 |
18.81 |
|
Non-vasectomized |
57.46.8 |
13.54 |
0.99 |
19.15 |
3.3
Relationships between trace elements in serum and prostatic fluid
The
interrelationship between trace elements in the serum and prostatic fluid
are summarized in Table 3 and 4. In general, the results were similar
in the vasectomized and the non-vasectomized groups. For example, a negative
correlation between the prostatic Zn (PZn) and prostatic Cd (PCd) levels
and a positive correlation between the prostatic Cu (PCu) and prostatic
Cd (PCd) levels were found in both groups. However there were exceptions.
No significant correlation was seen between the serum Cu (SCu) and serum
Cd (SCd) levels in the vasectomized group, while a significant negative
correlation existed in the control group. No significant correlation was
found between the PZn and SCd levels in the control group, whereas it
was significant in the vasectomized group. While there was no significant
correlation between the PCd and SCd levels in the control group, a significant
negative relationship was found in the vasectomized group.
Table
3. Spearman correlation coefficients for Zn, Cd, and Cu levels in prostatic
fluid (P) and serum (S) in vasectomized group. bP<0.05,
cP<0.01.
|
|
PZn |
PCd |
PCu |
SZn |
SCd |
| PCd |
-0.596c |
|
|
|
|
| PCu |
-0.083 |
0.380 |
|
|
|
| SZn |
0.270 |
0.073 |
0.144 |
|
|
| SCd |
0.414b |
-0.046c |
-0.297 |
-0.309 |
|
| SCu |
0.145 |
0.134 |
0.153 |
0.221 |
-0.097 |
Table
4. Spearman correlation coefficients for Zn, Cd, and Cu in prostatic fluid
(P) and serum (S) in non-vasectomized group. cP<0.01.
|
|
PZn |
PCd |
PCu |
SZn |
SCd |
| PCd |
-0.811c |
|
|
|
|
| PCu |
-0.230 |
0.540c |
|
|
|
| SZn |
0.319 |
0.254 |
0.345 |
|
|
| SCd |
0.276 |
0.258 |
-0.139 |
0.235 |
|
| SCu |
-0.045 |
0.097 |
0.077 |
0.382 |
-0.489c |
4
Conclusions
Zn
plays an important role in the development and maintenance of male reproductive
system. Zn is also considered to be an important antibacterial factor
in the prostate. It is of particular interest that decreased Zn or increased
Cd levels appear to be a risk factor for prostate cancer[6,7].
The intracellular content of Zn in malignant prostatic cells is only one
third of that of normal cells and this has been associated with elevated
testosterone levels within these cells[12]. The serum Zn level
was significantly lowered in patients with prostate cancer and elevated
in benign prostatic hypertrophy (BPH)[11,12].
Previously,
Zn and other trace element concentrations were usually measured by atomic
absorption spectroscopy (AAS). We employed a more advanced method, the
inductively coupled plasma-atomic emission spectroscopy (ICP-AES), which
could accurately and conveniently determine a series of elements at one
time. Our results on the prostatic fluid and serum Zn levels in the healthy
controls were identical with those in the literature where the traditional
AAS technique has been employed[13].
Marmar
et al[14] and Parish et al[15] have
reported that vasectomy does not influence Zn levels in the seminal plasma.
Their control subjects were, however, infertile or prostatitis patients.
Naik and associates[4] have indicated that seminal plasma Zn
levels were lower in vasectomized men having 1-8 years post-vasectomy
period than in non-vasectomized controls. In another carefully controlled
study, Jakobsen et al[5] observed that in men having
8 years post-vasectomy period, the seminal plasma Zn levels were significantly
lower as compared with non-vasectomized men (P<0.01).
The
present work shows that the influence of vasectomy on Zn levels in the
seminal plasma and prostatic fluid was different. Vasectomy reduced the
Zn level in the seminal plasma, but not in the prostatic fluid. As in
our experimental series, the seminal plasma and prostatic fluid Zn contents
were not assayed simultaneously, further investigation will be needed
to confirm this observation.
It
has been suggested that a possible relationship may exist between vasectomy
and elevated risk of prostate cancer and this possibility is stronger
in men vasectomized for more than 20 years post-vasectomy[16-18].
As Zn and Cd play a significant role in the genesis of prostate cancer,
it is reasonable to expect that their concentrations in vasectomized men
would be different from those of the controls. Our preliminary study showed
that higher PZn levels were found in men 20 years postvasectomy than
in men <20 years postvasectomy. The latter had a similar PZn level
as the controls. The incidence of BPH steadily rose after 50 years of
age and its incidence was estimated to be 50%-75% for men older than 60
years, and 80%-85%, older than 80 years[8]. It is also generally
accepted that BPH patients have higher prostatic Zn levels than men without
BPH. In the present study, the mean age of men 20 years post-vasectomy
was much higher than those in men <20 years post-vasectomy. Accordingly,
the incidence of BPH, as well as the PZn level should be higher in the
20 years group. The result in this study, however, were just the opposite,
ie, the PZn levels were lower in this group. Although a significance test
was not done due to the small number of subgroups, the inconsistency is
worthy of further investigation.
SZn
level were found to be significantly lower in the vasectomized than in
the non-vasectomized men. This difference seems more pronounced in men
<20 years post-vasectomy than in men 20 years post-vasectomy. The
tendency of time-dependent changes in the SZn levels appears to be inconsistent
with the PZn levels, but statistical analysis revealed no significant
interrelationship between SZn and PZn levels. In this regard, little has
been reported in the literature and further research is necessary.
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Correspondence
to Dr. Zeng-Nan MO, Department of Urology, First Affiliated Hospital,
Guangxi Medical University, Nanning 530027, China
Tel: +86-771-535 3266, ext 2516
E-mail: allan.mo@nn.col.com.cn
Received
2000-01-25 Accepted 2000-02-25
