The biological effect of phthalate esters on transabdominal migration of the testis in fetal rats in comparison with the antiandrogen flutamide.

Phthalate esters are commonly used as plasticizers for polyvinyl chloride and are known to be hormone-disrupting chemicals. We previously reported that mono-n-butyl phthalate (MBP) administered to rat fetuses induced cryptorchidism postnatally. The aim of this study was to investigate the biological effect of MBP on the transabdominal migration of the testis in prenatal rats by comparing this with the prenatal effect of the antiandrogen flutamide on testicular descent. Time-pregnant Wistar King A rats were divided into three groups: group I rats (N = 3) were administered MBP 0.3 g/day by gavage from gestational days 15 to 18; group II rats (N = 3) were injected with flutamide (30 mg/day) from gestational days 15 to 18; group III rats (N = 3) were administered solvent as controls. On the 19th gestational day, all rats underwent a cesarean section and the male fetuses were dissected to examine the position of the testis, which was significantly higher in the abdominal cavity in the MBP-treated rats than in either the flutamide-treated or control rats. No significant difference was observed in the position of the testis between the flutamide-treated and control rat fetuses. Our findings suggest that maternal MBP prevented transabdominal migration of the testis in prenatal rats, which may not have been due to either an antiandrogenic or estrogenic effect of MBP, but to a direct toxic effect of MBP on the testis.

Comparative studies of fertility and histologic development of contralateral scrotal testes in two rat models of unilateral cryptorchidism.

Fertility and the development of the contralateral scrotal testis in patients with unilateral cryptorchidism (UCO) remain controversial. This study investigated these controversies in two different UCO rat models using 43 Wistar King A rats. The animals were divided into three groups: I: an endocrinologic model of UCO was obtained by injecting pregnant dams with flutamide 100 mg/kg per day on days 15-17 of gestation (n = 12); II (n = 21): a mechanical model of UCO was obtained by extra-abdominal fixation of the gubernaculum in the neonatal period, III (n = 10): non-treated rats were used as controls. At the age of 90 days, 5 rats from each group were segregated into individual cages and housed with two virgin adult females for 2 weeks. The occurrence of pregnancy and litter sizes were counted in order to study fertility. All the animals were then weighed and killed. The occurrence of testicular descent, growth of the external genitalia, and epididymal development were examined. Morphologic and histologic evaluations were performed in the cryptorchid and contralateral testes. In the endocrinologic model (group I) the 10 female rats failed to show any offspring (0%), while in the mechanical model (group II) 9 out of 10 rats had offspring (90%, P < 0.001); 10 out of 10 control rats showed offspring. All of the rats in groups I and II had UCO, and the undescended testes were located in the superficial inguinal position, while the contralateral and control testes descended into the scrotum. Hypospadias and a small epididymis were frequently noted in the flutamide-treated rats. Testicular weight, seminiferous tubular diameter, and spermatogenesis were all significantly reduced in the undescended testes (UDT) compared to the contralateral and control testes. Moreover, the development of the contralateral testis was inhibited in group I compared to groups II and III. Our observations showed that short-term exposure to flutamide in utero induced significantly reduced fertility and degenerated contralateral scrotal testes in UCO rats compared to mechanically-induced UCO rats by early adulthood. It is suggested that fertility potential and testicular development in unilateral UDT may be partially due to the factors that induce testicular maldescent, especially in cases due to intrauterine hormonal abnormalities. These cases may show inhibited fertility and testicular development even after orchiopexy.

Does maternal stress induce abnormal descent of the testis in prepubertal rats?

OBJECTIVE: To investigate whether prenatal maternal stress, considered to alter plasma testosterone concentration and induce a lack of testosterone surge in male rat fetuses, has any effect on the growth of the processus vaginalis and testicular descent in male offspring. MATERIALS AND METHODS: Pregnant rats were divided into two groups. In group 1, the rats were placed three times daily for 60 min each session in Plexiglas rat holders (13x6x8 cm) illuminated by two 150-W flood lights from day 14 to day 18 of gestation during the dark phase of the animals' light (12 h) and dark (12 h) cycle. In group 2, pregnant females were not handled and acted as controls. After birth, the anogenital distance of both the male and female rats was measured, and the length of the processus vaginalis was measured at 7 days of age in some rats. Thereafter, at 21, 24, 27 and 30 days of age, testicular descent was assessed in the remaining male rats. RESULTS: In group 1, at 21, 24, 27 days of age, testicular descent was delayed in the stressed rats compared with the control rats. At 30 days of age, five of 36 stressed male offspring showed abnormal testicular descent; three testes were in the superficial inguinal position and two were above the scrotum. Both the anogenital distance and the length of the processus vaginalis were significantly less in the stressed male rats than in the controls. CONCLUSIONS: Maternal stress induced a female-like anogenital distance in male rat fetuses, and caused delayed and abnormal descent of the testis, by inhibiting the growth of the processus vaginalis after birth. Prenatal stress may therefore be involved in the delay of testicular descent in neonatal rats by inducing a mild anti-androgenic effect in the fetus.

Does proximal genitofemoral nerve division induce testicular maldescent or ascent in the rat?

OBJECTIVE: To investigate whether the division of the proximal genitofemoral nerve (GFN) in neonatal rats induces testicular undescent or ascent in adulthood. MATERIALS AND METHODS: Neonatal Wistar King A rats underwent a unilateral proximal GFN transection on either the right or left side. At the age of 30 days, testicular descent was examined in all rats and the position of the testis recorded. The animals were allowed to develop further and the position of the testis re-examined at the age of 90-180 days, when the testes were removed and weighed. Sham-operated rats were used as controls. RESULTS: At the age of 30 days, four of the 46 (9%) operated rats showed a unilateral undescended testis on the operated side. At the age of 90-180 days, 43 rats were re-examined (three rats died before re-examination); 34 (79%) of these rats showed undescended testes on the operated side. The occurrence of cryptorchidism was significantly higher in the 90-180-day-old mature rats than in 30-day-old prepubertal rats (P<0.01). The mean (sd) weight of the undescended testes, at 2.36 (0.21) mg/g body weight, was significantly less than that of the contralateral scrotal testes, at 3.83 (0.23) mg/g; P<0.01) and of the control testes at the age of 90-180 days. In the sham-operated rats, all testes were located at the bottom of the scrotum at 30 days of age and no rats showed any testicular ascent thereafter. CONCLUSIONS: The proximal division of the GFN in neonatal rats not only causes inguinoscrotal testicular maldescent but may also induce testicular ascent in adulthood. Testicular ascent may thus be caused by some intrauterine disorders of the GFN in patients with ascending testis.

Pubertal genitofemoral nerve division induces testicular ascent in adult rats.

BACKGROUND/PURPOSE: Ascending testes, which normally are located at the bottom of the scrotum in early infancy and later ascend back out of the scrotum, have been reported by several investigators. However, little is known about the effect of the division of the genitofemoral nerve (GFN) on testicular ascent as boys grow. The purpose of this study is to investigate whether the division of the proximal genitofemoral nerve in prepubertal rats induces testicular ascent in adulthood. METHODS: Thirty-day-old Wistar King A Rats (n = 27) underwent a unilateral proximal GFN transection on either the right or left side. At 150 days of age, the rats were killed, and their testicular position was examined. The length of the processus vaginalis was measured, and the testes were removed and weighed. Sham-operated rats were used as controls (n = 10). Student's t and the chi2 test were used for the statistical analysis. RESULTS: At 150 days of age, 21 of the 27 operated rats (77.8%) showed unilateral testicular ascent on the operated side. All testes were located at the bottom of the scrotum in sham-operated control rats (20 testes). Both the length of the processus vaginalis and the testicular weight were decreased significantly more on the operated side than in the sham-operated rats. CONCLUSIONS: These findings suggest that the proximal division of the genitofemoral nerve in prepubertal rats may induce a relative ascent of the testis by preventing the growth of the processus vaginalis in adulthood. In patients with such ascending testes, an abnormal development or accidental trauma of the genitofemoral nerve may be involved in testicular ascent.

Fertility and histological studies of the contralateral testes in two different intra- and extra-abdominal rat models of unilateral cryptorchidism.

OBJECTIVE: To investigate the effect of location of the testis on both testicular development and fertility in unilateral cryptorchidism. MATERIAL AND METHODS: Forty-nine Wistar King A newborn male rats were divided into three groups. In group 1 (15 rats) intra-abdominal unilateral cryptorchidism were created by the intra-abdominal fixation of the testis in the neonatal period. In group 2 (16 rats) extra-abdominal unilateral cryptorchidism was created by extra-abdominal fixation of the gubernaculum in the neonatal period. In group 3, 18 rats underwent a sham operation as controls. At 90 days of age, fertility was then assessed in each rat by housing it with two mature virgin females for 2 weeks. Thereafter, at 115-120 days of age, the rats were killed and their testes removed for histological examination. RESULTS: There was no significant difference in the pregnancy rate between females coupled with rats from any group, but the mean number of offspring was significantly lower in females coupled with rats in group 1 than in group 2. Furthermore, histological examination of both the cryptorchid and contralateral scrotal testes showed more severe changes in the intra-abdominal than the extra-abdominal testes. CONCLUSION: These results suggest that intra-abdominal cryptorchid testes are significantly more impaired than extra-abdominal cryptorchid testes, and that such impairment might be caused by exposure of the testis to a higher temperature. The more severely impaired undescended testes may thus induce the degeneration of the contralateral scrotal testis and thereby cause subfertility in the intra-abdominal unilateral cryptorchid rat model.

Fertility and histological studies in a unilateral cryptorchid rat model during early and late adulthood.

OBJECTIVE: To investigate the effect of age on fertility and testicular development in rats with untreated unilateral undescended testes. MATERIALS AND METHODS: Newborn male Wistar King-A rats were divided into two groups. In group 1, a mechanical model of unilateral undescended testis was created by performing extra-abdominal fixation of the gubernaculum in the neonatal period, and in group 2, sham-operated rats were used as controls. At 90 days old (early adulthood), the fertility of both groups was assessed by mating the rats with mature virgin females for 2 weeks. Thereafter, some of the rats were killed and their testes examined histologically, while the remaining rats were allowed to develop further. At the age of 180 days (late adulthood), fertility was re-assessed in the same way. All the rats were then killed and their testes removed for histological examination. RESULTS: There was no significant difference in pregnancy rate of females mated with males from either group in early adulthood. However, in late adulthood there was a significant reduction in pregnancy rate in females coupled with cryptorchid rats compared with that of females coupled with control rats. There was a significant degeneration of the unilateral cryptorchid testes compared with control testes in both early and late adulthood. In contrast, there were no significant changes in histological development between the contralateral scrotal testes and the controls in early adulthood, although they were significantly different from the controls in late adulthood. CONCLUSION: These results suggest that fertility is affected by ageing in untreated unilateral cryptorchidism; this may be induced by extensive damage not only in the undescended testes, but also in the contralateral scrotal testis, in this mechanically induced model of unilateral cryptorchidism.

Prenatal phthalate causes cryptorchidism postnatally by inducing transabdominal ascent of the testis in fetal rats.

Phathalate esters, which are commonly used as plasticizers for polyvinyl chloride, are also well known to disturb Sertoli cells. This study aims to show the effect of prenatally administered phthalate on testicular descent in pre- and postnatal rats. Pregnant rats were exposed to mono-n-butyl phthalate (MBP) by gavage from the 15th to the 18th gestational days. Rats administered with solvent only were used as controls. In 20-day-old fetuses (n = 15), the degree of transabdominal testicular ascent in relation to the bladder neck was thus found to be significantly higher in MBP-treated rats than that of the controls (n = 19). In addition, in MBP-treated male offspring (n = 26), 22 rats showed either bilateral or unilateral cryptorchidism at the age of 30 to 40 days old, and the occurrence of cryptorchidism was 84.6%. By contrast, the occurrence of cryptorchidism was 0% in the control rats (n = 15, P < .001). It is therefore suggested that prenatal exposure to MBP may disturb the Sertoli cells and elevate the fetal testes relative to the bladder neck while also inducing cryptorchidism postnatally. Sertoli cells may thus play an important role in the transabdominal descent of the testis by secreting Müllerian-inhibiting substance (MIS), which is known to act as a putative mediator of the transabdominal phase.

Extraabdominal fixation of the gubernaculum inhibits testicular descent in newborn rats.

Within 48 hours after birth, newborn rats were anesthetized, and the distal tip of the gubernaculum was exposed extraabdominally, then fixed to the fascia of the groin on the left or the right side under a dissecting microscope (6x). In the sham-operated rats, the distal tip of the gubernaculum was merely exposed. Nonoperated rats were used as controls. In 60- to 90-day-old operated rats (n = 42), all testes were located in the superficial inguinal position, and the incidence of cryptorchidism was 100% on the operated side. In the sham-operated rats (n = 28), 27 of 28 testes descended into the scrotum, and one was located in the perineum; the incidence of cryptorchidism was 3.6% on the operated side. All testes also descended into the scrotum, and the incidence of cryptorchidism was 0% in controls (n = 20). The incidence of cryptorchidism was significantly higher among operated rats than among sham-operated or control rats (P < .001). The testicular weight and the germinal epithelia of the cryptorchid testes were significantly lower than those of the scrotal testes in both sham-operated and control rats. Therefore it is suggested that the extraabdominal fixation of the distal tip of the gubernaculum in newborn rats induces cryptorchidism. The present model is considered to be a simple and useful one to investigate the process of testicular maldescent and inhibited growth of the testis in cryptorchidism.