Morphologic study of the testes from spontaneous unilateral and bilateral abdominal cryptorchid boars

Macroscopical and histological characteristics were examined in both testes from three healthy boars, three boars with unilateral abdominal cryptorchidism on the right side, and three boars with bilateral abdominal cryptorchidism. Abdominal cryptorchidism, unilateral and bilateral, provoked a significant decrease of the weight and volume of the ectopic testes. The scrotal testis of the unilateral cryptorchid boars showed an increase in its volume and weight. Cryptorchidism also induced abnormalities in the histological structure of seminiferous tubules, lamina propria, and interstitial tissue of the abdominal testes. The number of seminiferous tubules decreased; the seminiferous epithelium was constituted by few spermatogonia with an atypical pattern and by abnormal Sertoli cells. The lamina propria showed a variable degree of thickening and collagenization. The interstitial tissue was very developed but displayed a decrease in the Leydig cell population. These abnormalities were more critical in bilateral cryptorchidism than in unilateral cryptorchidism. The scrotal testis of the unilateral cryptorchid boars showed normal appearance, but a decrease of the number of seminiferous tubules was observed. Moreover, the seminiferous tubules showed impaired spermatid maturation. The alterations observed in the abdominal testes of the unilateral and bilateral cryptorchid boars were attributed to defective proliferation and differentiation of Sertoli cells and Leydig cells. The anomalies in the scrotal testis of the unilateral cryptorchid boars were due to disturbances in the Sertoli cell activity.     

Characterization of the semen quality of postpuberal boars with spontaneous unilateral abdominal cryptorchidism on the right side.

In recent studies, we found that the ectopic testis from postpuberal boars with unilateral abdominal cryptorchidism does not produce sperm. Therefore, in these males, the seminal characteristics can be used as indicators of the activity of the scrotal testis and its epididymis and also the accessory glands. The semen quality (ejaculate volume, cell-rich fraction volume, sperm concentration, sperm vitality, sperm motility, sperm morphology and cephalic stability of spermatozoa) was evaluated in healthy postpuberal boars and in postpuberal boars with unilateral abdominal cryptorchidism on the right side. In comparison with the healthy boars, the unilateral abdominal cryptorchid boars showed a significant decrease of the ejaculate volume, sperm concentration and sperm motility. The low sperm concentration indicated that unilateral abdominal cryptorchidism severely impairs the sperm production of the scrotal testis. The decrease of ejaculate volume was attributed to an abnormal activity of the accessory glands. The alterations in sperm motility develop as a result of dysfunctions in the epididymal epithelium and/or the accessory glands. The sperm vitality, sperm morphology and cephalic stability of spermatozoa maintained normal values; therefore, at testicular level, despite the low sperm production, the germ cell differentiation is not disturbed. At epididymal level, the morphological maturation of spermatozoa is not altered.     

Efficiency of the process of meiosis in scrotal testes of healthy boars and unilateral abdominal cryptorchid boars.

Unilateral abdominal cryptorchidism has usually been correlated with abnormalities in the spermatogenic activity of the scrotal testis. The present study describes the effects of unilateral abdominal cryptorchidism on the meiotic process in scrotal testes from postpubertal boars. The percentage of primary spermatocytes, secondary spermatocytes, and round spermatids was evaluated in testicular smears from scrotal testes of healthy boars and of right-sided unilateral abdominal cryptorchid boars. As compared to the scrotal testes of healthy boars, the scrotal testes of unilateral abdominal cryptorchid boars showed low transformation from primary to secondary spermatocytes (meiosis I), but normal transformation from secondary spermatocytes to round spermatids (meiosis II). The data obtained indicate that spontaneous unilateral abdominal cryptorchidism on the right side induced partial arrest of spermatogenesis at the primary spermatocyte stage that was attributed to anomalies in Sertoli-cell activity. Abnormal paracrine signals from altered Sertoli cells could have resulted in either disturbed mitosis, which led to the formation of spermatocytes with an abnormal DNA content, or abnormalities in the metabolic activity and the organization of the cytoskeleton of primary spermatocytes.     

Cytology of the interstitial tissue in scrotal and abdominal testes of post-puberal boars

The interstitial tissue of the testes from healthy boars, and unilateral and bilateral abdominal cryptorchid boars was examined by light and transmission electron microscopy. The left and right testes of healthy boars, and the left (scrotal) testis of unilateral cryptorchid boars had abundant mature Leydig cells, few fibroblasts and mast cells, scarce and small blood vessels, and little lymphatic areas. The right (abdominal) testis of unilateral cryptorchid boars contained abundant Leydig cells, fibroblasts and erythrocytes, scarce mast cells, and frequent blood vessels; Leydig cells exhibited either a mature but degenerative appearance or an immature appearance, and fibroblasts displayed immaturity signs. The interstitial tissue of the left (abdominal) testes of bilateral cryptorchid boars had small blood vessels surrounded by erythrocytes, lymphocytes, and few plasma cells, and abundant mature and immature Leydig cells, immature fibroblasts, and mast cells. Mature Leydig cells showed mid or advanced degeneration, and immature Leydig cells displayed either non-degenerative or degenerative patterns. The right (abdominal) testes of bilateral cryptorchid boars contained scarce immature Leydig cells in advanced degeneration, large fibrous and adipose areas, and blood vessels. These results indicated that unilateral abdominal cryptorchidism affect neither the structural nor the cytologic features of the interstitial tissue in scrotal testes. Unilateral and bilateral cryptorchidism induced abnormal differentiation of Leydig cells and fibroblasts leading to decreased steroid production and increased collagenization in abdominal testes.     

Changes in rat testicular adenylate cyclase activities and gonadotrophin binding during unilateral experimental cryptorchidism

Unilaterally cryptorchid rats were examined at 3, 8, 15, 22 and 28 days after operation. There was a selective decrease in the adenylate cyclase (ATP pyrophosphate--lyase (cyclizing), EC 4.6.1.1) responses to gonadotrophin stimulation in the abdominal testis. This was associated with a parallel decrease in specific FSH and LH binding. There was no reduction in the response of testicular adenylate cyclases to prostaglandin (PG) E-1 or fluoride stimulation, indicating that both the GTP binding protein (N-component) and the catalytic subunit of the adenylate cyclase complexes were intact. The reduction in FSH-responsive adenylate cyclase activity in the abdominal testis was not due to a change in the Km for adenylate cyclase activation, but was due to a reduction in maximal velocities. Unilateral cryptorchidism was also associated with a rapid decline in soluble Mn2+-dependent adenylate cyclase activity in germ cells (spermatids). By 3 days after operation there was an 82% decrease in germ cell adenylate cyclase activity. The loss of soluble Mn2+-dependent adenylate cyclase activity was associated with a parallel decrease in Sertoli cell secretion of androgen binding protein, indicating that Sertoli cell factors may be important for the maintenance of germ cell adenylate cyclase activity. The desensitization of the gonadotrophin--responsive adenylate cyclases and the loss of gonadotrophin receptors in Leydig and Sertoli cells were not due to changes in plasma gonadotrophin values because LH concentrations were within normal limits and plasma FSH was only marginally elevated in the cryptorchid rats. No significant alterations of any of these parameters were seen in the scrotal testis of unilaterally cryptorchid rats when compared to values for intact controls.     

Zinc metabolism in testicular feminization and surgical cryptorchid testes in rats

Rats with testicular feminization (Tfm) had been reported to have a testis specific zinc deficiency. In this report it is demonstrated that this organ specific zinc deficiency was not corrected by intraperitoneal zinc administration. Normal littermates on the other hand showed a positive testicular response to zinc administration. The increased testicular zinc level in control animals returned to normal 1 week after the zinc treatment probably due to the fast turnover of this element in the testis. Not only surgically induced cryptorchidism but also surgical cryptorchidism and epididymodeferentectomy (to simulate Tfm conditions in normal adult rats) caused a drastic reduction in testicular zinc level. Unlike in Tfm rats, however, the decrease in zinc content in operated animals was not accompanied by a corresponding decrease in alkaline phosphatase activity. Zinc concentration and alkaline phosphatase activity in plasma or other organs were not affected by the surgical procedure. The testicular copper content in the operated animals was higher than that of the unoperated controls.     

Regeneration of Leydig cells in unilaterally cryptorchid rats: evidence for stimulation by local testicular factors

Summary Leydig cells in testes of adult rats were selectively destroyed by a single intraperitoneal injection of ethane dimethane sulphonate. Four days later rats were made unilaterally cryptorchid and 1, 2 and 4 weeks later the histology of the testes was examined by light microscopy and morphometry. After induction of unilateral cryptorchidism, the volume of abdominal compared to scrotal testes was reduced by 45–60% due to rapid impairment of spermatogenesis in abdominal testes. Leydig cells were not present in either scrotal or abdominal testes in the 1-week unilateral crytorchid group. A new generation of foetal-type Leydig cells was observed in scrotal testes of the 2-week unilateral crytorchid group although their total volume per testis estimated by morphometry, was small, being approximately 1 l. In contrast, the abdominal testis exhibited a remarkable proliferation of foetal-type Leydig cells (total volume per testis, 16 l) which predominantly surrounded the peritubular tissues of the seminiferous tubules. A similar morphology and pattern of Leydig cell development was observed in scrotal and abdominal testes of the 4-week unilateral cryptorchid group where total Leydig cell volume was 7 l vs 21 l, respectively. The results show that regeneration of a new population of Leydig cells occurs more rapidly in the abdominal testis than in the scrotal testis of the same animal. These observations suggest the possibility that augmentation of Leydig cell growth is mediated by local intratesticular stimulatory factors within the abdominal testis. Development of new Leydig cells from the peritubular tissue provides circumstantial evidence that the seminiferous tubules and in particular the Sertoli cells, are a likely source of agents that stimulate the growth of Leydig cells.     

Surgically induced cryptorchidism-related degenerative changes in spermatogonia are associated with loss of cyclic adenosine monophosphate-dependent phosphodiesterases type 4 in abdominal testes of rats

The present study was undertaken to investigate the role of phosphodiesterase type 4 (PDE4) enzymes in cryptorchidism-induced apoptosis of the germ cells. Regulation of expression of PDE4 enzymes was studied in the abdominal and scrotal testes of surgically induced cryptorchid rats for 10, 20, and 30 days. In some cases orchidopexy was performed after 30 days of cryptorchidism, and rats were allowed to recover for an additional 50 days. Upon histological examination, marked degenerative changes in the epithelial lining of the seminiferous tubules within abdominal testes were observed compared with contralateral control or age-matched sham-operated rats. These changes included degeneration of some spermatogonia, apoptosis of the secondary spermatocytes, incomplete spermatogenesis, and lack of spermatozoa in the lumen. In contrast, contralateral scrotal testes exhibited normal histology. Significant improvement in the regeneration of spermatogonia was observed in rats after 50 days of recovery following orchidopexy. Immunocytochemical examination suggested the presence of PDE4A in germ cells while PDE4B was predominantly expressed on somatic cells. Western blotting using PDE4 subtype-selective antibodies showed the presence of two PDE4A variants (a 109-kDa PDE4A8 and a previously uncharacterized 88-kDa PDE4A variant) and two PDE4B (78-kDa PDE4B2 and 66-kDa PDE4B variant) bands. In unilaterally cryptorchid animals, the abdominal testis showed a time-dependent decrease in both PDE4A8 and 88-kDa PDE4A variants. In contrast, the expression of 66-kDa PDE4B was markedly increased in a time-dependent fashion in abdominal testes of cryptorchid rats. Animals surgically corrected for cryptorchidism and allowed to recover for 50 days exhibited normal expression of both PDE4A and PDE4B variants compared with aged-matched, sham-operated controls. In conclusion, this study suggests that down-regulation of PDE4A variants in cryptorchid testes may play an important role in the degeneration of spermatogonia and increased apoptotic activity in the germ cells.     

Changes of testicular cholesteryl ester hydrolase activity in experimentally cryptorchid rats

A simple and reliable method was developed to determine the neutral cholesteryl ester hydrolase (CEH) activity in rat testes, using cholesteryl-[1-14C]-oleate as substrate. The activity was due to a soluble enzyme present in the cytoplasm of predominantly Sertoli cells, which could be shown after depleting the testes of Leydig cells with ethane dimethyl sulphonate. This treatment also revealed that the loss of CEH activity in abdominal testes of experimentally cryptorchid rats takes place in the Sertoli cells. In prepubertal rats made unilaterally cryptorchid at birth, the CEH activity was significantly higher in the abdominal than in the scrotal testes at 16 days of age. This is earlier than any previously described biochemical change and coincides with, or may even precede, the earliest morphological changes which are accumulation of lipid droplets in the Sertoli cells. The testicular CEH activity then decreased to 30 days of age in the abdominal testes, whereas the activity increased in the contralateral, scrotal testes. When adult rats were made unilaterally cryptorchid for 24 h, the CEH activity decreased rapidly in the abdominal testes. These results suggest that a derangement in cholesteryl ester metabolism is an early event in the pathogenesis of testicular degeneration in cryptorchidism.     

Differences in aromatase activity between Leydig cells from the scrotal and abdominal testis in the naturally unilateral-cryptorchid boar

In an earlier study, estrogen production was much lower in Leydig cells from the abdominal than from the scrotal testis in naturally occurring unilateral cryptorchidism in the boar. A more direct assessment of aromatase activity was made in thirty-two mature male pigs to examine this observation further, using nonradioactive androstenedione (delta 4A 1.0 x 10(-6) M - 1.5 x 10(-5) M) and [1 beta, 2 beta-3H] delta 4A as substrates. Purified Leydig cells were prepared from normal boars and from unilaterally and bilaterally cryptorchid animals. Combined estrone sulfate (E1S) and estrone (E1) formation from delta 4A were measured by radioimmunoassay. Little or no estrogen secretion was seen with cells from the abdominal testis in unilaterally cryptorchid boars (n = 7), and E1S formation from delta 4A was 6- to 14-fold higher for scrotal cells (n = 6). Aromatase activity as reflected in percent conversion of substrate to [3H]-labeled water was clearly lower in cells from the abdominal testis (1.10 +/- 0.08 and 11.22 +/- 0.7%, respectively, p less than 0.01, n = 6). No marked reduction was noted for unilaterally cryptorchid boars with an inguinally located testis (10.18 +/- 0.27 and 13.09 +/- 0.58% for inguinal and scrotal testes, respectively, n = 3). Concentrations of E1S in testicular arterial and venous blood (n = 9) gave additional evidence of lower estrogen production by the undescended testis of the cryptorchid boar. It was concluded that lower aromatase activity is present in Leydig cells of the abdominal testis.     

Impaired detoxification of reactive oxygen and consequent oxidative stress in experimentally cryptorchid rat testis.

The effect of experimental cryptorchidism on the level of oxidative stress and antioxidant functions in rat testis was studied. Adult male Sprague-Dawley rats were rendered unilaterally cryptorchid (by suturing one testis to the abdominal wall) and killed 1, 3, or 7 days after the operation. As an indicator of oxidative stress, lipid peroxidation was measured by the diene conjugation method in testis homogenates. The activities of the antioxidant enzymes were determined either in the 10,000 x g supernatant fraction (glutathione [GSH] peroxidase, GSH transferase, hexose monophosphate shunt) or in crude testis homogenates (superoxide dismutase, catalase). An expected reduction (48%) in weight of the abdominal testes was evident by postoperative Day 7. The catalytic activities per testis of superoxide dismutase (Cu/Zn form) and catalase were found to decrease in cryptorchidism. The effect was seen on the first postoperative day and was most profound on Day 7 after surgery. The principal antioxidant enzyme, superoxide dismutase, was most sensitive to cryptorchidism, the activity in the abdominal testes being 74% or 85% (per gram of tissue or per whole testis, respectively; p less than 0.01). After impairment of the reactive oxygen detoxifying capacity, lipid peroxidation was increased in the abdominal testis by 46% (p less than 0.01) on postoperative Day 7. Slight concomitant increases were detected in the activities of GSH-peroxidase (p less than 0.01), GSH-transferase (p less than 0.001), and the hexose monophosphate shunt (p less than 0.001). This effect was seen only when calculated per gram of tissue, not per whole testis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Testicular steroid sulfatase in a cryptorchid rat strain

Steroid sulfatase (STS) activity was studied in scrotal and abdominal testes from genetically unilateral cryptorchid rats. Specific STS activity was significantly increased in microsomes from abdominal and scrotal testes of the cryptorchid animals as compared to that of control ones. When expressed per gonad, STS activity was only enhanced in the scrotal testis. No difference in the enzyme affinity was observed between descended and undescended testes. Testosterone content was markedly reduced in the abdominal testes. Normal plasma testosterone levels together with elevated LH levels were measured in the cryptorchid rats. The existence of differences in STS expression between descended and undescended testes gives additional support for this enzymatic activity being implicated in testicular function.     

Disruption of spermatogenesis is associated with decreased concentration of immunoreactive arginine vasopressin in testicular fluid

We have previously shown that testicular fluid contains factors that can inhibit luteinizing hormone (LH)-stimulated androgen production by Leydig cells, and others have reported the presence of immunoreactive vasopressin (iAVP) in the testes as well as in vitro inhibition by vasopressin of Leydig cell-androgen production. In the current report, we have used an established radioimmunoassay (RIA) to measure the concentration of iAVP in testicular fluid and have related changes in iAVP concentration to disruption of the seminiferous tubules. Spermatogenesis was disrupted in adult rats by surgically establishing bilateral cryptorchidism. The concentration of iAVP decreased progressively from 349 +/- 52 to 61 +/- 5 pg/ml during 4 wk. When cryptorchidism was unilaterally established, the concentration of iAVP in fluid from that testis decreased to 116 +/- 19 pg/ml while the concentration of iAVP in the contralateral scrotal testis remained unaffected. Unilateral ligation of the ductuli efferentes also caused an equivalent unilateral decrease in iAVP to 110 +/- 15 pg/ml. The osmotic pressure of the testicular fluid was not altered by disruption of gametogenesis, and the extracellular "albumin space" was not increased. Therefore, the decrease in concentration of iAVP was probably not due to dilution with increased amounts of interstitial fluid. We conclude that the disruption of spermatogenesis is associated with a decrease in the concentration of iAVP in testicular fluid and suggest that AVP or a similar peptide may be involved in the intratesticular mechanisms associated with increased production of androgen by Leydig cells after disruption of spermatogenesis.     

Clinical, morphological and endocrinological aspects of cryptorchidism in the horse

The authors analysed clinical, histological and hormonal data obtained from 205 cryptorchid horses. The majority of the unilaterally and bilaterally retained testes were located in the inguinal canal; however, the ratio of inguinal vs abdominal retention appeared to decrease with advancing age. In unilateral cryptorchidism, a pronounced preference was noted for left abdominal retention, whereas for inguinal cryptorchids, the retained testes occurred equally on both sides. Right inguinal retention was found to decrease with advancing age. Histology of cryptorchid testes revealed apparently normal Leydig cells and arrested spermatogenesis. Plasma testosterone concentrations were similar in normal stallions and unilateral cryptorchids, even in those which had the scrotal testis removed. Plasma oestradiol-17beta levels were lower in unilateral cryptorchids than in stallions.     

Cryptorchidie et température testiculaire

The testis migrates to a scrotal location before birth. This physiological descent is associated with a reduction in the temperature of the testicular environment since the temperature of the scrotal cavity is lower than that of the body one. This leads to the etablishment of a themperature gradient between the testis and the body which already exists in prepubertal boys. In cases of testicular maldescent (cryptorchidism), the temperature of the testis in its cryptorchid location is much higher than that of the normally descended contrlateral testis. However, there are no data obtained from human studies to establish wether the increased temperature of a cryptorchid testis is responsible for the spermatogenic perturbations typically observed. Nor do we know wether the relocation of a cryptorchid testis to the scrotum permits re-establishment of a normal testicular temperature. Adult men with a history of cryptorchidism constitute about 10% of infertile men, and among these previously cryptorchid infertile men 45% have an abnormally elevated scrotal temperature. This abnormal increase in scrotal temperature is a negative risk factor for fertility: these men have smaller testicular volumes, a more severely impaired spermatogenesis and a higher prevalence of primary infertility than previously cryptorchid infertile than previously cryptorchid infertile men with normal scrotal temperature. However, data provided until now do not allow to know whether elevated temperature is due to the decreased testicular size (hypotrophy) or is a consequence of cryptorchidism per se.     

Follitropin receptors in rat testis. Characterization with enzymatically 125I-labeled human follitropin.

The interaction between enzymatically radioiodinated human follitropin and the follitropin receptors in testis homogenate was investigated in immature and adult rats. The 125I-labeled human follitropin exhibited high binding activity with specific binding of up to 17% in the presence of an excess of testis homogenate. Approx. 50% of the bound hormone could be eluted at pH 5, and the receptor purified tracer exhibited a 3.6-fold increase in binding activity when compared with the original tracer preparation. Quantitative analysis of equilibrium binding data was performed with corrections for the measured specific activity and maximum binding activity of the tracer hormone. The equilibrium association constants (Ka) determined 24 degrees C were not significantly different in immature and adult rat testis, and the mean value for Ka was 3.9 . 10(9) M-1. At 37 degrees C, the Ka value obtained using immature rat testis was 1.3 . 10(10) M-1. The association of 125I-labeled human follitropin with immature rat testis homogenate was time and temperature dependent. In the presence of an excess of unlabeled hormone, 30--60% of the preformed hormone . receptor complex was dissociated after 24 h incubation. A specific and sensitive radioligand-receptor assay for follitropin was developed using immature rat testis homogenate. The minimum detectable dose of purified human follitropin was 0.6 ng, and human urinary and pituitary follitropin, ovine follitropin and pregnant mare serum gonadotropin reacted in the assay with equivalent slopes. The potencies of highly purified pregnent mare serum gonadotropin and highly purified human follitropin were similar in the radioligand-receptor assay, consistent with the follitropin bioactivity of the equine gonadotropin.     

A comparison of Leydig cell function after unilateral and bilateral cryptorchidism and efferent-duct-ligation

Surgical induction of cryptorchidism or ligation of the efferent ducts disrupts spermatogenesis. The response of Leydig cells to disrupted gametogenesis was studied in vitro in tissue and collagenase dispersed Leydig cells obtained from the testes of rats that were made unilaterally or bilaterally cryptorchid or had been efferent-duct-ligated. Four wks after surgery, androgen secretion per mg of tissue or per Leydig cell in response to maximal luteinizing hormone (LH) stimulation was greater in tissue from damaged than from sham-operated testes. It was concluded that disruption of spermatogenesis resulted in Leydig cells that were hyperresponsive to LH stimulation in vitro. Unilateral lesions produced different responsiveness of Leydig cells from the testes ipsilateral and contralateral to the lesion, supporting the hypothesis that intragonadal modulation of Leydig cells function occurs when the function of seminiferous tubules is impaired. Stimulated androgen production of Leydig cells from the contralateral nonligated testis did not differ from that of the sham-operated controls. With unilateral cryptorchidism, which is accompanied by an increase in the temperature of the operated testis, Leydig cells from the scrotal testis were also hyperresponsive compared to those from sham-operated controls. This suggests a possible intergonadal influence of aspermatogenesis caused by cryptorchidism.     

Influence of experimental cryptorchidism on cholesterol side-chain cleavage enzyme and delta5-3beta-hydroxysteroid dehydrogenase activities in rat testes.

Testicular cholesterol side-chain cleavage enzyme (CSCCE) and delta5-3beta-hydroxysteroid dehydrogenase (delta5-3beta-HSD) activities were assessed 12 hours and 2, 4, 8, 16, and 32 days after surgical induction of bilateral cryptorchidism in adult rats. Within 12 hours after surgery CSCCE activity (expressed as dpm of isocaproic acid-14C formed from cholesterol-26-14C/3 hours/testis) was significantly reduced (P less than 0.01) in cryptorchid testes to approximately 55% of sham-operated control values and remained depressed at less than 50% of control activities 2, 4, 16, and 32 days after surgery. Cryptorchid testis delta5-3beta-HSD activity (measured by a pregnenolone substrate-depletion assay and expressed as mumoles of products/30 minutes/testis) did not differ from controls (P greater than 0.05) 1/2, 2, or 4 days after translocation of testes to the abdominal cavity. By day 8 of cryptorchidism, however, delta5-3beta-HSD activity was reduced to 60% of control values (P less than 0.05) and continued to decline to approximately 30% of controls during the remainder of the experimental period. These observed alterations in enzyme activities suggest an impairment in the ability of cryptorchid rat testes to synthesize androgens and further indicate that testicular CSCCE is more acutely sensitive to the cryptorchid milieu than delta5-3beta-HSD.     

Effect of cryptorchidism on steroidogenic and mitogenic activities in rat testicular interstitial fluid

There was a significant (P less than 0.05) and consistent increase in the potency of steroidogenic stimulatory activity (testosterone production by purified Leydig cells in vitro) in testicular interstitial fluid of the cryptorchid compared to the scrotal testis from 1 to 4 weeks after the induction of unilateral cryptorchidism. In contrast, the level of mitogenic activity [( 3H]thymidine incorporation into 3T3 cells) was not significantly different between interstitial fluid from cryptorchid and scrotal testes for up to 4 weeks after surgery. These results indicate that the steroidogenic activity and the mitogenic activity are due to different, as yet unidentified, factors in testicular interstitial fluid.     

Follitropin receptors in rat testis characterization with enzymatically 125I-labeled human follitropin

The interaction between enzymatically radioiodinated human follitropin and the follitropin receptors in testis homogenate was investigated in immature and adult rats. The ¹²⁵I-labeled human follitropin exhibited high binding activity, with specific binding of up to 17% in the presence of an excess of testis homogenate.Approx. 50% of the bound hormone could be eluted at pH 5, and the receptor purified tracer exhibited a 3.6-fold increase in binding activity when compared with the original tracer preparation. Quantitative analysis of equilibrium binding data was performed with corrections for the measured specific activity and maximum binding activity of the tracer hormone. The equilibrium association constants (K_a) determined at 24°C were not significantly different in immature and adult rat testis, and the mean value for K_a was 3.9 · 10⁹ M^?1. At 37°C, the K_a value obtained using immature rat testis was 1.3 · 10¹⁰ M^?1. The association of ¹²⁵I-labeled human follitropin with immature rat testis homogenate was time and temperature dependent. In the presence of an excess of unlabeled hormone, 30–60% of the preformed hormone · receptor complex was dissociated after 24 h incubation. A specific and sensitive radioligand-receptor assay for follitropin was developed using immature rat testis homogenate. The minimum detectable dose of purified human follitropin was 0.6 ng, and human urinary and pituitary follitropin, ovine follitropin and pregnant mare serum gonadotropin reacted in the assay with equivalent slopes. The potencies of highly purified pregnant mare serum gonadotropin and highly purified human follitropin were similar in the radioligand-receptor assay, consistent with the follitropin bioactivity of the equine gonadotropin.