Yonago Acta medica 1997;40:79–89

A Novel Mechanism to Explain the Detrimental Effect of Left Cryptorchidism on Right Testicular Functions
Kouji Ono and Nikolaos Sofikitis
Department of Urology, Faculty of Medicine, Tottori University, Yonago 683, JapanThe effect of unilateral cryptorchidism on ipsilateral testicular function has been wellstudied in human and experimental animals. However the effect of unilateral cryptorchidism on contralateral testicular function has remained unclear. To evaluate theeffect of left cryptorchidism on right testicular function, an experimental model was
created in 2 groups of immature male rats (group A, 19 rats; and group C, 7 rats).
Seven male rats of the same age were sham-operated (groups B and D). Twenty-eightdays after the operation, bilateral epididymal caudal sperm content and motility,
bilateral testicular weight, bilateral epididymal caudal weight, seminal vesicular weight,
right testicular versus intra-abdominal temperature difference (RDT), fertility rate,
right epididymal caudal sperm acrosin profile, testosterone response to human chorionicgonadotropin stimulation and mean seminiferous tubular diameters of bilateral testes
were tested. They were significantly lower in group A than in group B (Student’s t-test;
P < 0.05). In contrast, the concentrations of serum luteinizing hormone and follicle
stimulating hormone were significantly higher in group A than in group B (Student’s ttest; P < 0.05). Four months after the operation, right testicular blood flow wassignificantly higher in group C than in group D (Student’s t-test; P < 0.05). These
results indicate a bilateral Leydig cell secretory deficiency in rats with unilateralcryptorchidism results in the impaired spermatogenic process and epididymal sperm
maturation process. This effect may be explained by the elevation of the right testiculartemperature as a result of an increase in testicular blood flow.
Key words: cryptorchidism; fertility; testicular function; testicular blood flow; testicular temperature

Cryptorchidism, which is the most common
disorder of sexual development at full-term
birth, is often associated with infertility or subfertility and is the major risk factor for testicularcancer (Lipshultz et al.,1976; Chilvers et al.,1984). Since the work of John Hunter in 1756,
both clinical and experimental evidences suggest that fertility is impaired in unilateral cryptorchidism (Alpert et al., 1983; David et al.,
1992; Seppo et al., 1996).
It is generally accepted that a relatively low
temperature is preferable in spermatogenesis in

mammalian species. Actually, it has beenreported that temperature in the scrotum was 4–
5˚C lower than that in the abdomen (Harrison etal., 1949). Waites (1961) measured the temperature of the abdominal aorta and testicularartery at various points, and found that thetemperature of the testicular artery was lower
than that in the abdominal cavity by 5.2˚C atseveral points. Thus, a great effect of the intratesticular temperature on spermatogenesis has
been demonstrated (David et al., 1981; Nagler
et al., 1987). It is well known that the function

Abbreviations: ABP, androgen binding proteins; BAPNA, N-a-benzoyl-DL-arginine-p-nitroanilide; BWW,
Biggers-Whitten-Whittingham; FSH, follicle stimulating hormone; hCG, human chorionic gonadotropin;
LH, luteinizing hormone; RDT, right testicular versus intra-abdominal temperature differences; rFSH, rat
FSH; STD, seminiferous tubular diameter; TAA, Total acrosin activity

79

K. Ono and N. Sofikitis

didymal caudal sperm content and motility,
bilateral testicular and epididymal weight,
seminal vesicular weight were measured. The
right epididymal caudal sperm acrosin profile,the presence of bilateral epididymal caudal
cytoplasmic droplets, and anti-sperm antibodies
were also evaluated, and the bilateral testes
were examined histologically. Four months
after the operation, the rats of groups C (n = 7)
and D (n = 7) were examined to determine testicular blood flow by using the previously described method (Hurt et al., 1986).

of the cryptorchid testis is impaired by a temperature rise in unilateral cryptorchidism. The
effect of unilateral cryptorchidism on ipsilateral
testicular function has been well studied inhuman and experimental animals. However,
the effect on contralateral testicular function
has not been studied completely (Dariusz et al.,1992).
We hypothesized that the function of thecontralateral testis is impaired by temperaturerise in unilateral cryptorchidism, and studied
the mechanism on an experimental model of theleft cryptorchidism in rats.

Testicular temperature
Materials and Methods

Bilateral testicular temperature was assessed by
percutaneus insertion of a 29-gauge needle
probe attached to a digital thermometer (Unique
Medical, PTC201 model, Tokyo). Intraabdominal temperature was monitored with arectal probe and body temperature was maintained between 36.7 and 37.3˚C with radiantheat throughout the procedure. The difference
between the intra-abdominal and intratesticulartemperature was recorded by the method described previously (Sofikitis et al., 1992).

The experiments were performed on 4-weekold immature male Wister rats weighing 80–
100 g. The rats were divided into 4 treatmentgroups: A and C) cryptorchid; B and D) shamoperated. Rats were made left cryptorchidthrough a left dorsolumbar incision by suturing
the left testis to the lower pole of the ipsilateralkidney with 2 interrupted 6-0 nylon sutures
under Nembutol (25 mg per kg body weight)
anesthesia. Sham operations consisted of a left
dorsolumbar incision, exposure and replacementof the left testis, and closure of the incision using
the same anesthesia. Before the surgical procedures we evaluated the difference between theright testicular and the intra-abdominal temperatures. Twenty-eight days after the operation, the groups A (n = 19) and B (n = 7) were
examined for abdominal temperature, right testicular temperature and fertility. The concentrations of testosterone, luteinizing hormone(LH) and follicle stimulating hormone (FSH)
were determined in blood aspirated from theinferior vena cava by a midline abdominal
incision. The incision was closed and all therats received human chorionic gonadotropin(hCG) (1000 units; Mochida Phamceutical Co.,Tokyo, Japan) by intraperitoneal injection.
Three hours after hCG stimulation, testosterone
response was evaluated for blood aspirated
from the same vein. Then, all the rats were sacrificed by an injection of saturated potassium
chloride into the left venticle. Bilateral epi-

Fertility Assessment
Two fertile female Wistar rats (2 months old) inthe 1st h of estrus as determined by vaginal
smear examination were placed in a single cagewith each male rat. The female rats were checked after mating to detect spermatozoa in theirvaginas by microscopic examination of thevaginal fluid. Females in which spermatozoa
were detected were then checked 3 times daily
from day 21 for parturition (day 1 was designated as the day of mating). A male rat was considered fertile if its mating resulted in at least
one pregnancy.

Determination of the weight of the testes,
epididymides and seminal vesicles
The testes, epididymides and seminal vesicles
were excised, dissected free of surrounding
tissue, and weighed on a Mettel Basbal scale(Delta Range, Tokyo).
80

Left cryptorchidism and testicular function(0.12 M NaCl, 0.025 M HEPES) to remove thesoluble proteinase inhibitors in semen thatinterfere with acrosin activity. The sperm pellet
was subsequently suspended in buffer that hadi) detergent, which facilitated disruption of theacrosomes and released the acrosomal enzymes(Triton X-100, Sigma Chemical Co., St. Louis,MO); ii) basic pH, which allowed activationof proacrosin into enzymatically active acrosin;
and iii) synthetic arginine amide substrate [N-abenzoyl-DL-arginine-p-nitroanilide (BAPNA);
Sigma Chemical Co.], which, when hydrolyzed, released a chromophoric product. The total
amount of color developed after 3 h incubation
was measured spectrophotometrically.
TAA was expressed as µIU/10 6 sperm: 1
IU of acrosin activity was defined as the amountof enzyme that hydrolyzed 1 µmol of BAPNA
per minute at 23˚C. A change in absorbance of
9.9 at 410 nm corresponds to the hydrolysis of
1.0 µmol of BAPNA.

Epididymal sperm content, quantitative
sperm motility (%motility), qualitative
sperm motility (motility grade) andbilateral epididymal caudal cytoplasmic
droplet presense
Each epididymis was separated carefully fromits testicle under a magnification of 10, provided by a stereo zoom microscope (model TL2,
Olympus Corp., Tokyo). The epididymis was
divided into 3 segments: the head, the body andthe tail. The epididymal tail was trimmed andminced in 5 mL of Biggers-Whitten-Whittingham(BWW) medium adjusted to pH 7.4 at 37˚C with
6-M sodium hydroxide. The minced epididymal tissue was then separated from the liberated
spermatozoa by filtration through a stainlesssteel wire mesh with a pore size of 80–100 µm.
Six droplets of the filtrate was used for the
sperm count (number of spermatozoa/mL
BWW medium) and the average number was
calculated. The sperm count was determinedwith a Makler counting chamber (Sefi Medical
Instruments, Haifa, Israel). The chamber wasplaced on the slide of an ordinary microscope,and a 20-power objective and 10-power eyepiece were used. Ten droplets of the filtrate
were counted to calculate the percentage ofmotile spermatozoa imediately after its preparation, so that the estimate of motility became
more accurate. The proportion of motile spermatozoa was counted for all the cells in thechamber. Motility was also graded microscopically and assigned a value from 0 to 4, with 0
representing no movement and 4 representing
the maximum perceived motility. Samples formotility evaluation were stored on a warming
tray at 35˚C in the viewings. Bilateral epididymal caudal cytoplasmic droplet rates werecounted by laser microscope.

Antisperm antibody assay
The immobilization test was done for the antisperm antibody assay as described by Isojima
and colleagues (1968). Small volumes of guinea pig complement were added to epididymal
sperm solutions, and the mixture was incubatedfor 30 min before microscopic evaluation. The
percentages of motile and non-motile sperm
were determined for each serum of cryptorchidism and a negative control. A rat was considered positive for the immobilizing antibodies
if the percentage of motile sperm was less thanhalf that of the negative control.

Determination of serum testosterone concentration
Testosterone concentration was determined byradioimmunoasssay using a kit (Nihon DPC
Corporation, Tokyo) according to the methodof Coyotupa and coworkers. The intra- andinter-assay coefficients of variation were 5.5
and 9.2%, respectively. The sensitivity of theassay was 0.1 ng/mL.

Acrosin activity assay
Total acrosin activity (TAA) of the spermatozoa was measured as described by Zaneveld andcolleagues (1972). In brief, the spermatozoa
were washed free of seminal plasma by centrifugation at 6,000 × g for 20 min over Ficoll
81

K. Ono and N. Sofikitis∆) between intra-abdominal and right intra-testicular temperature, presTable 1. Difference (∆ence of anti-sperm antibody, and fertility
Group

n

Temperature∆(˚C)
Preoperation
Postoperation

A: Cryptorchid 19
4.1 ± 0.4
B: Control
74.2 ± 0.3
Values are expressed as mean ± SD.
*P < 0.05 compared with the control group.

Number of rats
Anti-sperm antibody positive

Fertile

9*
0

2*
7

3.1 ± 0.6*
4.1 ± 0.4

mCi/g suspended in 10% Dextran containing
0.05% Tween 80. After 5 min of agitation, 0.15
mL of microsphere suspension (40,000–60,000
microspheres) was drawn into a plastic syringe
designed for placement in a gamma radiation
counting vial, and analyzed in a gamma counter.
This suspension was injected into the left
ventricular catheter over 20 s and flushed with
1.0 mL saline (0.9%). Blood was withdrawn
from the femoral artery catheter using a constant withdrawal sage pump for 10 s before theinjection of microspheres, during the injection,and thereafter for a total withdrawal time of 70 s
(to 0.8 mL). The blood sample was placed in a
preweighed counting vial and withdrawal rate
was determined. The rats were killed using a
potassium chloride injection into the left ventricle. The right testis was removed, weighed, andanalyzed for radioactivity in the gamma counteralong with the blood sample and the empty
injection syringe as described previously(David et al., 1981). Blood flow (BF) was
calculated using the following formula:

Determination of serum LH and FSH concentration
Serum levels of LH and follicle stimulating
hormone (FSH) were measured with double
antibody radio-immunoassay methods. LH wasassayed with a rat LH [125I] assay system fromAmersham International plc (Amersham, United Kingdom). The intra- and inter-assay coefficients of variation were 6.5 and 7.2%, respectively. The sensitivility of the assay was 0.8 ng/
mL. FSH was assayed with a rat FSH (rFSH)[125I] assay system from Amersham International. The intra- and inter-assay coefficients ofvariation were 4.2 and 7.0%, respectively. The
sensitivity of the assay was 0.9 ng/mL.

Histology
Testicular tissue was fixed in Bouin’s solution.
The 5-µm thick sections were obtained andstained with hematoxylin and eosin. The diameters of the seminiferous tubules were determined by an ocular micrometer. The 10 mostcircular tubules were measured in each specimen. The mean seminiferous tubular diameter(STD) was calculated in microns for each testis
as described previously (Salman et al., 1988).

BF = (R × T)/B
where BF = blood flow in milliliters per minute;R = rate of withdrawal of blood in milliliters per
minute; B = number of counts blood sample; T= number of counts in tissue sample. BF was
divided by the weight of the right testis to determine flow per gram of tissue.

Testicular blood flow
Rats were anesthetized with sodium pentobarbital (25 mg per kg body weight) and weremaintained at a body temperature of approximately 37˚C. Testicular blood flow was determined using strontium 85-labeled microspheres(15 ± 1.1 µm) with a specific activity of 9.0

Statistical analysis
The data were analyzed with Student’s t-test at
5% level of significance.

82

Left cryptorchidism and testicular function

Table 2. Weight of the testis, epididymis and seminal vesicle (mg)
Group

n

TestisRight

Epididymis
Left

A: Cryptorchid 19 1003 ± 163*
263 ± 102*
B: Control
7 1198 ± 81
1193 ± 87
Values are expressed as mean ± SD.
*P < 0.05 compared with the control group.

Results

Seminal Vesicle

Right

Left

85.9 ± 27.4*
119.3 ± 16.3

44.7 ± 24.1*
133.1 ± 19.2

310 ± 130.9*
477.4 ± 78.4

rats (Table 2). The right testicular weights incryptorchidism rats were also significantly lower than in the control group.

Testicular temperature
Results were significant between righttesticular versus intra-abdominal temperature
differences (RDT) within the cryptorchid andthe control groups (Table 1). The cryptorchidism group showed a significantly smaller
RDT value compared with the control group.

Weights of epididymis and seminal vesicles
Left epididymal caudal weight was significantly lower than right epididymal caudal
weight in the cryptorchidism group (Table 2).
The right epididymal caudal weights in thecryptorchidism group were significantly lower
than in the control group. Seminal vesicularweight in the cryptorchidism group was significantly lower than in the control group.

Presence of antisperm antibody
The positive reactions of the antisperm antibody
were obtained in 9 sera of 19 cryptorchidism rats,
but in no sera of control rats (Table 1).

Epididymal sperm content
Fertility

The sperm content was significantly lower bilaterally in the cryptorchid rats than in the control group (Table 3).

The effects on fertility are summarized in Table
1. All the control rats were proved to be fertile.
On the other hand, fertile rats in the cryptorchidgroup were only 2 out of 19 and significantly
lower than the controls.

Quantitative and qualitative assessmentof sperm motility
The percentage of motile sperm and the motility
grade were significantly lower bilaterally in thecryptorchid rats than in the control group (Table
3).

Testicular weight
Left testicular weight was significantly lower
than right testicular weight in cryptorchidism

Table 3. Sperm concentrations, motility and forward progresion score from the cauda epididymis
Group

n

Concentration (×106/mL)
Right
Left

A: Cryptorchid 19
25.0 ± 16.5*
6.5 ± 8.5*
B: Control
747.8 ± 7.1
43.3 ± 6.2
Values are expressed as mean ± SD.
*P < 0.05 compared with the control group.

Motility (%)
Right
Left
17.7 ± 16.4*
58.4 ± 10.383

3.4 ± 7.3*
61.2 ± 9.1

Forward progresion (0–4)
Right
Left
1.2 ± 0.4*
1.6 ± 0.4

0.3 ± 0.2*
1.4 ± 0.3

K. Ono and N. Sofikitis

Table 4. Right epididymal caudal total sperm acrosin activity (TAA) and cytoplasmic droplet
presence (CDP) in the epididymal caudal sperm
Group

n

TAA
(µIU/106 sperm cells)

A: Cryptorchid
1931.1 ± 9.1*
B: Control
748.4 ± 10.3
Values are expressed as mean ± SD.
*P < 0.05 compared with the control group.

CDP (%)
Right

Left

41.8 ± 6.2*
16.3 ± 4.2

70.3 ± 10.2*
15.1 ± 4.8

Table 5. Serum hormone levels and testosterone response to hCG stimulation
Group

n

LH
(ng/mL)

A: Cryptorchid
1917.8 ± 7.4*
B: Control
79.3 ± 1.6
Values are expressed as mean ± SD.
*P < 0.05 compared with the control group.

Testosterone (ng/mL)
Pre-hCG
Post-hCG

FSH(ng/mL)1.63 ± 0.89*
1.72 ± 0.34

0.7 ± 0.2*
0.3 ± 0.1

4.39 ± 2.1*
7.15 ± 0.81

elevated in the cryptorchid rats compared to thecontrol group. Serum hCG-stimulated testosterone levels were significantly lower in thecryptorchid rats than in the control group.

Acrosin activity
TAA was significantly lower in the cryptorchidrats than in the control group (Table 4).

Epididymal caudal cytoplasmic droplet
presense

Sertorli cell function

The presence of cytoplasmic droplets shows theimmature spermatozoa in cauda epididymis.
The percentage of epididymal caudal cytoplasmic droplets were significantly higher bilaterally in the cryptorchid rats than in the control group (Table 4).

Serum FSH levels are included in this section as
a function of Sertoli cells because it may indirectly reflect inhibin production by the testis,which has been shown to be suppressed in
cryptorchidism (Au et al., 1983). The cryptorchid rats showed significantly elevated FSH
levels compared to the control group (Table 5).

Leydig cell functions

Testicular blood flow

Serum testosterone levels were slightly lower inthe cryptorchid rats than in the control group(Table 5). Serum LH levels were significantly

Right testicular blood flow was significantly
higher in the cryptorchid rats than in the control
group (Table 6).

Histology
Table 6. Right testicular blood flow
Group

n

Testicular histology was evaluated under lightmicroscopy (Fig. 1). There was no difference inthe structures of seminiferous tubules between
the descended contralateral testes and the control group (data not shown). The seminiferous
tubules were completely and fully differentiated and stratified in a control rat testis (Fig.

Blood flow
(mL/min 100 g testis)

C: Cryptorchid
7
43 ± 8*
D: Control
732 ± 7
Values are expressed as mean ± SD.
*P < 0.05 compared with the control group.

84

Left cryptorchidism and testicular function

niferous tubules were composed of some Sertoli
cells and a few spermatogonia. Numerous processes of Sertoli cells and degenerative cells
were shown in the lumen. The mean seminif-

1A). Spermatozoa was shown in some of thetubules. However, the number of germinal cells
were remarkably decreased in the undescended
testes in cryptorchid rats (Fig. 1B). The semi-

Fig. 1. Light micrograph of an 8-week-old rat testis. A: Control. Seminiferous tubule is completely fully
differentiated and stratified. Spermatozoa are shown in some of the tubules. × 100. B: Left cryptorchid rat left testis.
Germinal cells in the undescended testes are remarkably decreased in number. Seminiferous tubules are composedof some Sertoli cells and a few spermatogonia. Numerous processes of Sertoli cells and degenerative cells areshown in the lumen. × 100.

85

K. Ono and N. Sofikitis

Sertoli cells. Therefore, the elevation of theblood level of FSH caused by the cryptorchid
testis permitted us to speculate on the hypofunction of Sertoli cells (Au et al., 1983). Ourdata confirms the results of the study of theimpairments in spermatogenesis and Sertoli cellfunction published by Karpe and colleagues(1981). The present data showed that Leydig
cell function was impaired by the elevation ofserum LH level, the reduction of testosterone
level and the much lower testosterone response
to hCG stimulation in the immature cryptorchidrats (Table 5). The hyporesponsivity of hCG
may be related to a decreased sensibility of thetestis to hCG based on the decline of LH receptors expressed on the Leydig cells of cryptorchidrats. The elevated serum LH levels associatedwith subnormal testosterone levels suggests theexistence of a state of compensated Leydig cell
failure virtually identical to the adult cryptorchid testis. In this state, elevated levels of LH
are required to enable the testicular output of
testosterone to be maintained in the normal
range (Jegou et al., 1984). And it also suggeststhat the recovery of serum testosterone levels
may be related to the increase of the total number of Leydig cells (Risbringer et al., 1981).
The results in the present study also confirmed that the abdominal versus right intratesticular temperature difference, the testicularweight, the epididymal sperm content, and the
motility of epididymal spermatozoa are reduced
after 4 weeks of induction of a unilateral left
cryptorchidism (Jegou et al., 1984; Hurt et al.,1986). Many investigators have shown that experimental left varicocele leads to a contralateral increase in testicular blood flow (Davidet al., 1981; Nagler et al., 1987; Turner and
Lopez, 1990), increases intratesticular temperature (David et al., 1981; Turner and Lopez,
1990), and decreased spermatogenesis (Davidet al., 1981; Hurt et al., 1986) or semen quality(Al-Juburi et al., 1979). Increased testiculartemperature is probably subsequent to theincrease in testicular blood flow (Turner et al.,1993). Increased testicular blood flow is also a
possible cause for lower intratesticular testosterone concentration and impairment of spermatogenesis (Nagler et al., 1987). This is the

Table 7. Comparative mean seminiferus
tubular diameters (µm) of right and left testes
Group

n

Right testis

Left testis

A: Cryptorchid 19 230.5 ± 10.5* 120.3 ± 8.9*
B: Control
7 260.4 ± 12.4 258.7 ± 11.5
Values are expressed as mean ± SD.
*P < 0.05 compared with the control group.

erous tubular diameters of bilateral testes in thecryptorchid rats were significantly lower than in
the control group (Table 7).

Discussion
In many studies on experimental cryptorchidism, 2- or 3-week-old rats have been used
(Jegou et al., 1984; David et al., 1992). However, in our preliminary experiments using 3week-old rats, we found that the testes were
movable, endocrine data were not reproducible,
and local hemorrhagic necrosis in the testes occurred by injury during the measurement of
intra-testicular temperature. Hence, we used 4week-old rats for our study. Our study demonstrated that cryptorchidism induced in the immature rats before sexual maturation resulted ina significant impairment in all testicular functions, including spermatogenesis, Sertoli celland Leydig cell functions.
Regarding the seminiferous tubules of thecryptorchid testis, the diameter was significantly shorter than that in the control rats, spermatids were markedly decreased, and complex,
thin, long cellular processes of Sertoli cells anda small number of spermatogonia were only
observed in the testicular epithelium (Fig. 1);
spermatogenesis was also impaired (Table 3).
In our present experiment, neither androgenbinding proteins (ABP) nor inhibin were
measured, but it is well known that Sertoli cells
are the target of FSH. Sertoli cells produce
ABP and estrogen under the control of FSH,
and these products participate in spermatogenesis. At the same time, inhibin which is
involved in the feedback mechanism for the
regulation of FSH secretion is produced by86

Left cryptorchidism and testicular function

first report of an increase in contralateral testicular blood flow and temperature on experimental unilateral cryptorchidid rats. The significant decrease in the weights of the epididymis and seminal vesicles in the cryptorchid rats
indicates lower levels of androgens in blood,
because these glands are androgen dependent(Price and Williams-Ashman, 1961). However,
it is compatible with the findings of the Jegou
and colleagues (1984) who noted no significant
differences in epididymal weight. These differences may be due to the different experimental
observation periods or to the difference speciesof rats used. The significant bilateral decreasein testicular weight in the cryptorchid rats
indicates bilateral testicular dysfunction withrespect to both spermatogenesis and androgenproduction, since it has been suggested that
testicular size has a direct correlation with thefunction (Takihara et al., 1987).
The present study strongly supports the
hypothesis that the increase in right testiculartemperature is associated with the increased testicular blood flow and it may develop the righttesticular damage in the rats with left cryptorchidism.
Previous studies have shown significant evidence of a reduction in spermatogenesis inunilateral cryptorchid rats as determined by thecaluculation of sperm concentrations in fluid
from the tail of the epididymis (Juenemann etal., 1986; David et al., 1992). In the present
study, we observed the severe reduction in
fertility of unilateral cryptorchid rats. However, the effect of unilateral cryptorchidism
on fertility cannot be determined by studying
the changes in the standard semen analysis topredict the sperm fertilizing potential(Menkveld et al., 1990). Several assays have
gradually been developed to evaluate different
functional parameters of the spermatozoa
beyond the standard sperm parameters; adenosine triphosphate of spermatozoa (Comhaire etal., 1987), cervical mucus penetration assay(Pretorius et al., 1984), human hemizona attachment assay (Oehninger et al., 1989), zona freehamster egg penetration (Wolf et al., 1983),
triple staining (Talbot et al., 1980), spermatozoal acrosin activity and hypoosmotic swelling

test (Zaneveld et al., 1990) are the most popularof these tests. Acrosin, a serine proteinase,associated with the sperm acrosome appears to
be involved in the acrosome reaction, as well as
the ability of spermatozoa to bind to and penetrate the zona pellucida. Acrosin levels inhuman ejaculates are significantly correlatedwith their capacity to fertilize oocytes in vitro(Tummon et al., 1991). The present study confirms the earlier finding that there was a positive correlation between acrosin activity andfertility (Felice et al., 1994). Total acrosin activity and fertility were significantly lower inthe unilateral cryptorchid rats compared to thecontrols. It seems that the impairment on fertility is indicative of lower total acrosin activity inthe unilateral cryptorchid rats. Antisperm antibody is also known to affect sperm penetration
ability and sperm oocyte interaction (Ronald,1994). It may contribute to reduced fertility inthe unilateral cryptorchid rats.
In conclusion, our study suggested that thedysfunction of the Leydig cell was caused byweight loss of the right testis due to temperaturerise with the increased blood circulation in theright testis, and the fertility was reduced by impairment of spermatogenesis in the seminiferous tubules and epididymal sperm maturationby the decreased androgen.
Acknowledgments: The authors thank Prof. Ikuo
Miyagawa, Department of Urology, Faculty of
Medicine, Tottori University, for valuable advice
concerning the design of this study.
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(Received December 20, 1996, Accepted January 28, 1997)89