Characterization of epidermal growth factor receptor in testis, epididymis and vas deferens of non-human primates

Venlafaxine increases aromatization, reduces apical V-ATPase in clear cells and induces increased number of mast cells and smooth muscle cells death in rat cauda epididymis

Depressive disorders (DD) have affected millions of people worldwide. Venlafaxine, antidepressant of the class of serotonin and norepinephrine reuptake inhibitors, has been prescribed for the treatment of DD. In rat testes, venlafaxine induces testosterone (T) aromatization and increases estrogen levels. Aromatase is a key enzyme for the formation of estrogen in the epididymis, an essential organ for male fertility. We investigated the impact of serotonergic/noradrenergic venlafaxine effect on the epididymal cauda region, focusing on aromatase, V-ATPase and EGF epithelial immunoexpression, smooth muscle (SM) integrity and mast cells number (MCN). Male rats were distributed into control (CG; n = 10) and venlafaxine (VFG, n = 10) groups. VFG received 30 mg/kg b.w. of venlafaxine for 35 days. The epididymal cauda was processed for light and transmission electron microscopy (TEM). The expression of connexin 43 (Cx43) and estrogen alpha (Esr1), adrenergic (Adra1a) and serotonergic (Htr1b) receptors were analyzed. Clear cells (CCs) area, SM thickness, viable spermatozoa (VS) and MCN were evaluated. Apoptosis was confirmed by TUNEL and TEM. The following immunoreactions were performed: T, aromatase, T/aromatase co-localization, V-ATPase, EGF, Cx43 and PCNA. The increased Adra1a and reduced Htr1b expressions confirmed the noradrenergic and serotonergic venlafaxine effects, respectively, corroborating the increased MCN, apoptosis and atrophy of SM. In VFG, the epithelial EGF increased, explaining Cx43 overexpression and basal cells mitotic activity. T aromatization and Esr1 downregulation indicate high estrogen levels, explaining CCs hypertrophy and changes in the V-ATPase localization, corroborating VS reduction. Thus, in addition to serotonergic/noradrenergic effects, T/estrogen imbalance, induced by venlafaxine, impairs epididymal structure and function.

Expression and localization of epidermal growth factor, transforming growth factor-α and epidermal growth factor receptor in the canine testis

Gene expression of epidermal growth factor (EGF), transforming growth factor-α (TGF-α) and EGF receptor (EGF-R) and the localization of the corresponding proteins in the canine testis were studied. Levels of mRNA expressions were determined by semiquantitative reverse transcription polymerase chain reaction in the testes of the peripubertal (4–6 months), young adult (3–4 years), advanced adult (7–8 years) and senescent (11–16 years) groups. The EGF-R mRNA level in the testes of the peripubertal group was significantly higher than those in the other groups, whereas there was no difference in EGF and TGF-α mRNA levels among groups. Immunohistochemical stainings for EGF, TGF-α and EGF-R in the testis revealed that immunoreactivity in the seminiferous epithelium and Sertoli cell was weak and nonspecific for the stage of spermatogenesis, and distinct staining was found in Leydig cells. These results suggest that the EGF family of growth factors may be involved in testicular maturation and function in the dog.

Epidermal growth factor regulates connexin 43 in the human epididymis: role of gap junctions in azoospermia

BACKGROUND

Gap junctions (GJs) allow for direct communication between adjacent cells. They are composed of connexons consisting of transmembrane proteins, connexins (Cxs). The objectives of this study were to determine if GJ proteins GJA1 (Cx43), GJB1 (Cx32) and GJB2 (Cx26) are present in the epididymis of men with a normal epididymis, to assess whether or not Cx expression and localization are altered in azoospermic patients, and to determine if epidermal growth factor (EGF) regulates GJA1 expression.

METHODS

Epididymides were obtained from men with localized testis cancer with active spermatogenesis and histologically normal epididymal tubule (group 1), men with non-obstructive azoospermia secondary to Sertoli-cell only syndrome (group 2) and from azoospermic men with normal spermatogenesis and epididymal obstruction (group 3). Epididymides were subdivided into three segments: caput, corpus and cauda. Quantitative real-time RT-PCR was performed to assess GJA1, GJB1, GJB2 and EGF receptor (EGFR) mRNA levels in epididymides from patients from each group (all n=3, except n=1 for caput blockage). A human caput epididymal cell line was then used to determine the role of EGFR signaling on the regulation of human epididymal GJA1.

RESULTS

Real-time RT-PCR analysis revealed that GJA1, GJB1, GJB2 and EGFR were expressed along the human epididymis. In the cauda epididymidis of group 2 and 3 men, we observed a significant decrease in GJA1 (P=0.0456 and P=0.0465, respectively) and GJB1 (P=0.0450 and P=0.0497, respectively) mRNA levels when compared with group 1 men. We also observed a decrease in EGFR mRNA levels (P=0.0358) in the cauda epididymidis of group 3 men when compared with group 1. Immunocytochemistry revealed that in the epididymis, GJA1 and EGFR were localized between basal and principal cells and between adjacent principal cells. In group 2 and 3 patients, however, we noted a dramatic increase in cytosolic immunostaining for both GJA1 and EGFR in both principal and basal cells. Using a human caput epididymal cell line derived from fertile men, we demonstrated that changes in GJA1 phosphorylation could be regulated by EGF (P=0.015) and the extracellular regulated kinase 1/2 signaling pathway (P=0.03). Furthermore, while the phosphoinositide-3-kinase (PI3K)/AKT signaling pathway did not alter GJA1 phosphorylation, treatment with PI3K/AKT inhibitor LY294002 significantly (P=0.024) inhibited the EGF-stimulated increase in GJA1 total protein levels at 24 h. Immunolocalization indicated that loss of PI3K/AKT signaling was associated with increased cytosolic localization of Cx43 in this cell line.

CONCLUSIONS

Together, these data suggest that in azoospermic men decreased expression of EGFR may be responsible for decreasing GJA1 levels and increasing its cytosolic localization via the PI3K/AKT signaling pathway.

Androgenic regulation of novel genes in the epididymis

The epididymis is critically dependent on the presence of the testis. Although several hormones, such as retinoids and progestins, and factors secreted directly into the epididymal lumen, such as androgen binding protein and fibroblast growth factor, might play regulatory roles in epididymal function, testosterone (T) and its metabolites, dihydrotestosterone (DHT) and estradiol (E2), are accepted as the primary regulators of epididymal structure and functions, with the former playing the greater role. To ascertain the molecular action of androgens on the epididymis, three complementary approaches were pursued to monitor changes in gene expression in response to different hormonal milieux. The first was to establish changes in gene expression along the epididymis as androgenic support is withdrawn. The second was to determine the sequence of responses that occur in an androgen deprived tissue upon re-administration of the two metabolites of T, DHT and E2. The third was to study the effects of androgen withdrawal and re-administration on gene expression in immortalized murine caput epididymidal principal cells. Specific responses were observed under each of these conditions, with an expected major difference in the panoply of genes expressed upon hormone withdrawal and re-administration; however, some key common features were the common roles of genes in insulin like growth factor/epidermal growth factor and the relatively minor and specific effects of E2 as compared to DHT. Together, these results provide novel insights into the mechanisms of androgen regulation in epididymal principal cells.

Localization of the epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR) in the bovine testis

In the last few decades, several growth factors were identified in the testis of various mammalian species. Growth factors are shown to promote cell proliferation, regulate tissue differentiation, and modulate organogenesis. In the present investigation we have studied the localization of EGF and EGFR in the adult bovine testis by means of immunohistochemical method. Our results demonstrated that EGF and EGFR were localized solely to the bovine testicular germ cells (spermatogonia, spermatocytes, and round spermatids). In contrast, the somatic testicular cells (i.e., Sertoli, Leydig, and myofibroblast cells) exhibited no staining affinity. EGF and EGFR were additionally detected in the epithelial lining of straight tubules and rete testis. Interestingly, the distribution of EGF and EGFR in the germ cells was mainly dependent upon the cycle of the seminiferous epithelium since their localization appeared to be preponderant during the spermatogonia proliferation and during the meiotic and spermiogenic processes. In conclusion, such findings may suggest that EGF and EGFR are important paracrine and/or autocrine regulators of spermatogenesis in bovine.

Effects of epidermal growth factor on sperm content and motility of rats with surgically induced varicoceles

AIM

To investigate the effect of epidermal growth factor (EGF) on the sperm content and motility of the varicocelized rats.

METHODS

Forty-eight male Wistar rats were randomly divided into five groups. Experimental varicocele was induced by partial ligation of the left renal vein in the varicocele, the varicocele repair, the varicocele with EGF and the varicocele repair with EGF groups, whereas the control group only received a sham induction of varicocele. Surgical repair of varicocele was performed 4 months later in the varicocele repair and varicocele repair with EGF groups. EGF administration was performed daily by s.c. injection in the varicocele with EGF and varicocele repair with EGF groups at the dose of 10 microg/(kg.day) from the next day of the second surgery. One month later, all animals were killed and bilateral cauda epididymal sperm counts and motility were evaluated.

RESULTS

The mean sperm count and percentage of motile spermatozoa were significantly higher bilaterally in the varicocele with EGF group than in the varicocele group (P < 0.05). They were also significantly higher bilaterally in the varicocele repair with EGF group than in the varicocele repair and the varicocele with EGF groups (P < 0.05).

CONCLUSION

EGF can improve bilateral epididymal sperm content and motility of the rat with surgically induced varicocele. The administration of EGF in combination with surgical repair is more effective than surgical repair or EGF administration alone. EGF might be useful for the treatment of infertility induced by varicocele.

Seasonally activated spermatogenesis is correlated with increased testicular production of testosterone and epidermal growth factor in mink (Mustela vison)

Seasonal changes in spermatogenesis were studied with respect to testicular production of both testosterone and epidermal growth factor (EGF) in mink. The testes were collected in November (n = 15; testis recrudescence), February (n = 15; before breeding season), March (n = 14; breeding season), and May (n = 11; testis involution) and the following parameters of testicular activity were quantified: testicular mass, number of testicular spermatozoa, percentages of haploid, diploid, and tetraploid (G2/M-phase) cells and content of testosterone and EGF. The growth factor was immunohistochemically localized in the parenchyma. Testis mass, spermatogenic activity, and the production of both testosterone and EGF were maximal in March, but were not significantly different from the levels in February. The correlation between testis weight and sperm per testis was r = 0.825 (P < 0.001). Testosterone and EGF levels were correlated to each other (r = 0.78; P < 0.001) and had significant positive correlations to testis mass, number of sperm and proportion of haploid cells; and negative correlations to percentages of mitotic cells. EGF was localized in interstitial cells and in the luminal region of seminiferous tubules, where it occurred during the last steps of spermiogenesis. We inferred that intensified seasonal spermatogenesis was stimulated by testosterone and by autocrine/paracrine effects of EGF.

Growth Factor-Stimulated Mitogen-Activated Kinase (MAPK) Phosphorylation in the Rat Epididymis Is Limited by Segmental Boundaries1

Previous evidence has shown that sperm maturation is the result of successive events that influence sperm cells as they move through different microenvironments from the caput to the cauda epididymis. The physiological basis for the creation and maintenance of specific microenvironments along the epididymis are poorly understood. Anatomically, the epididymis consists of segments or lobules of epididymal tubule separated by connective tissue septa (CTS). The fact that CTS restrict the diffusion of tracer substances between segments and that certain gene expression patterns are segment-specific suggest that segments may represent functional epididymal units. In this report, we have further investigated epididymal segmentation by focusing on the ability of CTS to limit the effect of biologically relevant molecules, in particular epidermal growth factor (EGF), basic fibroblast growth factor (FGF2), and vascular endothelial growth factor A (VEGFA), in Segments 1 and 2 of the rat epididymis. We have demonstrated that these growth factors activate mitogen-activated kinase (MAPK) in both segments studied and that growth factors injected into the interstitial space of these segments in vivo exhibited a stimulatory effect only in the segment into which they were injected, i.e., MAPK activation was not observed in the adjacent segment. This restricting influence of CTS was abrogated by treatment with collagenase. In addition, we demonstrate the expression of selected forms of these growth factors and their receptors in Segments 1 and 2, and identify potential downstream targets. These results suggest that CTS regulate the trophic influences of growth factors and potentially other paracrine molecules, thus creating functionally separate units within the epididymis.

EFFECT OF EPIDERMAL GROWTH FACTOR ON SPERMATOGENESIS IN THE CRYPTORCHID RAT

PURPOSE

Epidermal growth factor (EGF) is secreted mainly from the submandibular glands. Submandibular gland ablation causes a marked decrease in male fertility, which suggests that EGF influences spermatogenesis. We investigated the effect of EGF in combination with orchiopexy on cryptorchid rat testes in which tubular deterioration had become partially irreversible.

MATERIALS AND METHODS

Unilaterally cryptorchid rats were obtained by daily administration of 7.5 mg flutamide (Nihonkayaku, Tokyo, Japan), an androgen receptor antagonist, to pregnant rats. At age 10 weeks the unilaterally cryptorchid rats underwent orchiopexy with or without EGF administered into the cryptorchid testis. EGF solution (10 microg/ml) was delivered into the seminiferous tubules by retrograde perfusion through the rete testis. At 14 days testicular recovery was assessed based on the maturity of spermatogenesis using a modified Johnsen score and from the number of apoptotic germ cells per seminiferous tubule.

RESULTS

Mean Johnsen score +/- SEM was significantly higher in the orchiopexy with EGF than in the orchiopexy without EGF group (7.85 +/- 0.12 vs 7.12 +/- 0.13, p <0.001). The number of apoptotic germ cells tended to be smaller in the orchiopexy with EGF group than in the orchiopexy without EGF group (0.16 +/- 0.05 vs 0.28 +/- 0.08).

CONCLUSIONS

Although orchiopexy for cryptorchidism partly improved spermatogenesis, recovery was limited. EGF administered in combination with orchiopexy was more effective for spermatogenesis than orchiopexy alone. This may be applicable in patients with cryptorchidism.

Autocrine regulation of steroidogenic function of Leydig cells by transforming growth factor-alpha

We have determined the effects of LH on the expression of transforming growth factor-alpha (TGFalpha) and epidermal growth factor receptor (EGFR) system in rat Leydig cells and investigated its role in steroidogenesis. LH and TGFalpha/epidermal growth factor (EGF) significantly increased the levels of TGFalpha mRNA and protein, and the levels of EGFR protein in immature rat Leydig cells (ILC). Treatment with TGFalpha or EGF for 24h resulted in significant increase in androgen production in ILC. The increase in androgen production in response to TGFalpha was associated with increased mRNA levels of SR-BI, steroidogenic acute regulatory (StAR) and P450scc but not of 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and P450c17. TGFalpha also caused a marked increase in the levels StAR protein in ILC. EGFR inhibitor (AG1478) blocked the effects of TGFalpha while MEK-inhibitor (PD98059) potentiated TGFalpha or LH effects on steroidogenesis. A PKA inhibitor (H89) blocked both TGFalpha and LH effects on steroidogenesis. We conclude that TGFalpha plays an autocrine role in LH dependent development and function of Leydig cells.

The effect of sustained and local administration of epidermal growth factor on improving bilateral testicular tissue after torsion

Epidermal growth factor (EGF) modulates Leydig cell proliferation, steroidogenesis, spermiogenesis, and Sertoli cell activity. It plays an important role in repairing ischemia-reperfusion injury in different tissues. The aim of this study was to evaluate the effects of sustained and local administration of EGF on improving bilateral testicular tissue after torsion. A total of 57 Wistar albino rats were used. For the EGF transport system, 1x2 cm gelatin films containing 2 microg EGF were used. Torsion was created by rotating the right testis 720 degrees in a clockwise direction for 4 h in all groups except the control group. Then, in the torsion group, bilateral orchiectomy was performed. After returning the torsioned ipsilateral testes to their normal state, the bilateral testes were wrapped by 1x2 cm unloaded gelatin films in the gelatin (G7 and G21) groups and, by 2 microg EGF loaded gelatin films in the EGF 7 and EGF 21 groups. The testes were removed on the seventh and 21st days, respectively, for biochemical and histological examination. Histologically, Johnsen's spermatogenesis criteria and mean seminiferous tubule diameter (MSTD) measurements were used. The EGF7 group did not show significant loss of Sertoli cells, while in the G7 group the number of these cells decreased. The ipsilateral ischemic testis of the EGF21 group showed Leydig cell hyperplasia, and the contralateral non-ischemic testes in this group were similar to the control group. In the G21 group, the bilateral testes showed Sertoli cell only syndrome in some sections, and most of the cells were undergoing apoptosis. The mean spermatogenesis scores and MSTD in the EGF7 and EGF21 groups were higher than in the G7 and G21 groups ( P<0.05). Malondialdehyde levels were significantly lower in the EGF groups than in the G groups ( P<0.05). Glutathione peroxidase (GSH-Px) levels in the G21 group were significantly higher than in the EGF21 group. Our study shows that local and sustained EGF release after testicular torsion improves bilateral testicular injury. EGF administration may be a new treatment choice for bilaterally injured testis after detorsion without removing the twisted testis.

Sodium-inorganic phosphate cotransporter NaPi-IIb in the epididymis and its potential role in male fertility studied in a transgenic mouse model

Analysis by cDNA microarrays showed that in the murine epididymis, NaPi-IIb was the predominantly expressed epithelial isoform of the sodium-inorganic phosphate cotransporter and was markedly overexpressed in the proximal region in the infertile knockout (KO) compared to the fertile heterozygous (HET) c-ros transgenic mouse. The apparent up-regulation in the KO mouse confirmed by Northern and Western blot analyses could be explained by the absence of NaPi-IIb from the initial segment of the HET epididymis, as revealed by immunohistochemistry, and its presence on the epithelial brush border throughout the proximal epididymis of KO mice, where differentiation of the initial segment fails to occur. Both NaPi-IIb mRNA and protein were scarce or absent from the cauda epididymidis of both genotypes. A high content of inorganic phosphate was measured enzymatically in the HET cauda luminal fluid, with a 27% decrease in the KO mice. This decrease, presumably from a greater reabsorption of inorganic phosphate, particularly in the initial part of the KO epididymis, may disturb the normal process of sperm maturation in these infertile males. By contrast, no apparent consequences were observed for the transport of Na+ and Ca2+, the concentrations of which (approximately 26 mM and approximately 30 microM, respectively) were measured by microelectrodes to be identical in the caudal fluid from both genotypes.

Systemic proliferative changes and clinical signs in cynomolgus monkeys administered a recombinant derivative of human epidermal growth factor

Epidermal growth factor (EGF) effects have been explored extensively in vivo in rodents, but little is known about trophic responses in nonhuman primates. A previous publication reports the hyperplastic epithelial/parenchymal changes noted in the digestive tract (tongue, esophagus, stomach, intestine, liver, gallbladder, pancreas, and salivary glands) of adult cynomolgus monkeys treated with recombinant human EGF(1-48) (rhEGF(1-48)). This report documents clinical findings and structural effects in the remaining epithelium-containing tissues of these animals. Two monkeys/sex/dose received rhEGF(1-48) by intravenous bolus at 0 (vehicle), 10, 100, 500 (females only), or 1,000 microg/kg/day (males only) daily for up to 2 weeks. Treatment- and dose-related clinical findings included emesis, fecal alterations (soft feces and diarrhea), lacrimation, nasal discharge, hypoactivity, transient hypotension, and salivation after dosing. Male monkeys administered 1,000 microg/kg became moribund after 5 days of treatment and were necropsied. All other monkeys completed the 2-week treatment period. Necropsy findings in nongastrointestinal tissues were: enlarged, pale kidneys at 100 microg/kg and greater; small thymuses seen sporadically at all doses; and enlarged adrenals and small thyroids in males at 1,000 microqg/kg. Respective organ-to-brain weight ratios at 500 and 1,000 microg/kg for kidneys were 1.5- and 2.6-fold greater and for heart were 1.7- and 1.3-fold greater than controls. Microscopically, pronounced dose-related epithelial hypertrophy and hyperplasia were evident in kidney, urinary bladder, skin (epidermis and adnexa), mammary gland, prostate, seminal vesicles, epididymis, uterus, cervix, vagina, thyroid, thymus, tonsillar crypts, cornea, trachea, and pulmonary airways. Epitheliotrophic effects were conspicuous in many tissues at 100 to 1,000 microg/kg. Changes to renal collecting ducts were present at 10 microg/kg, suggesting that kidneys were a relatively sensitive target. Proliferative alterations were not apparent in testes, intraocular structures, brain ependyma and choroid plexus at any dose. Aside from the noted exceptions, rhEGF(1-48) was a pantrophic epithelial mitogen in cynomolgus monkeys when used intravenously at suprapharmacologic doses.

Testis epidermal growth factor and spermatogenesis

Epidermal growth factor (EGF) is a cytokine that promotes cell proliferation, regulates tissue differentiation, and modulates organogenesis. Although a rich source of EGF is the submaxillary gland, many tissues produce this cytokine, including the testis. Leydig cells are the principal source of EGF in the testis. On attainment of sexual maturation the germ cells, primarily spermatocytes and round spermatids, form EGF with the onset of spermatogenesis. EGF appears to be involved in the development of the testis and in spermatogenesis. The expression of the EGF gene in rat testis was determined by the application of the RT-PCR method and testis RNA as substrate. The results suggest that EGF produced by Leydig cells and germ cells may modulate spermatogenesis as an autocrine and/or paracrine factor.

Comparative regulation of alpha1-adrenergic receptor mediated contraction in urogenitally derived smooth muscle. Effect of epidermal growth factor

Contractility of smooth muscle within mammalian urogenital organ systems has an established role in physiological/pathophysiological functioning of the component structures. Our aim was to examine the direct effect of epidermal growth factor (EGF) on smooth muscle tone as well as its indirect effects in regulating alpha1-adrenoceptor-mediated contraction of the prostate, the vas deferens and renal arteries. Tissues were mounted isometrically, under controlled conditions, and changes in tension in response to treatment with phenylephrine (PE) with or without pretreatment with EGF were recorded on a physiological recorder via force transducers. In the rabbit prostate, EGF potentiated the magnitude of contraction to PE. The potentiation appeared to be dependent on cyclo-oxygenase products. In the human prostate, EGF potentiated the contractile response to PE. EGF had no effect on the PE-induced contraction of the rabbit renal artery and vas deferens. EGF alone did not alter smooth muscle tone in any of the above-mentioned tissues. The main finding of this study is the difference in the regulation by EGF of the alpha1-adrenoceptor-mediated response in smooth muscle of the prostate, from that by the vas deferens and renal artery. The reasons for this difference in response remain to be elucidated. This study may form the basis for further investigation into receptor transregulation and its relevance to symptomatic benign prostatic hyperplasia (BPH).

Cellular distribution of EGF, TGFalpha and their receptor during postnatal development and spermatogenesis of the boar testis

The epidermal growth factor (EGF), the transforming growth factor alpha (TGFalpha) and the epidermal growth factor receptor (EGFr) have been immunolocalized, (i) during the testicular postnatal development (i.e. at the perinatal, prepubertal and adult periods), and (ii) during the seminiferous epithelium cycle in the different germ cell types. While TGFalpha was essentially observed in somatic cells, specifically in perinatal Leydig cells and in mature Sertoli cells, EGF was localized both in germ cells and in somatic cells with a preferential tubular expression. Furthermore, identification of EGFr in different testicular cell types indicates that during postnatal development and spermatogenesis, testicular cells are potentially responsive to EGF in that they express EGFr. Indeed, in the course of the gonadal development, the EGFr distribution was evidenced both in somatic and germ cells with a specific germ cell pattern depending upon the seminiferous epithelium cycle. A predominant EGFr staining was evidenced during the meiotic process and the spermiogenesis. Together, the present data are in favor of the involvement of the TGFalpha/EGF system in the local control of testicular cells during development and particularly of its potential direct implication in crucial steps of spermatogenesis such as meiosis and spermiogenesis.

Immunohistochemical localization of the epidermal growth factor-receptor in rhesus-monkey prostate

Epidermal growth-factor receptor (EGF-r), a membrane-bound glycoprotein activated by EGF, is important in maintaining the integrity and function of the prostate. To investigate EGF-r presence in the prostate of the rhesus monkey, monoclonal-antibody immunohistochemical examination was performed. The monkey prostate consisted of the cranial and caudal lobes, and the prostatic epithelial cells were composed of the secretory and basal cells. The distribution patterns of EGF-r in the prostatic epithelial cells were quite different between the cranial and caudal lobes. In the caudal lobe, EGF-r was seen in both secretory and basal cells, whereas, in the cranial lobe, the EGF-r was seen exclusively in the basal cells. The stromal cells of both lobes did not show EGF-r. This study revealed that each prostatic lobe contains specific binding sites for EGF, indicating a biological difference between the two lobes of the prostate of the rhesus monkey.

Relationship between submandibular gland epidermal growth factor and spermatogenesis in C3H mice

Epidermal growth factor (EGF), a potent mitogen produced primarily in the submandibular gland of adult male mice, has been implicated in modulating processes known to be of vital importance in the regulation of spermatogenesis. In the present investigation we demonstrate that submandibular gland EGF from adult male mice is indeed capable of displacing radiolabeled EGF from testicular membranes. Scatchard analysis of this binding site reveals that it is of high affinity (Kd = 0.77 nM) and low capacity (Bmax = 8.15 fmol/mg protein). Cross-linking of 125I-EGF to the identical membrane preparation resulted in the SDS-PAGE/autoradiography identification of a single band at approximately 170 kDa. Next, we examined the cellular distribution of the EGF receptor in the testis using biotin-streptavidin immunoperoxidase and employing different antisera probes generated to a conserved sequence of the EGF receptor. The Scatchard and cross-linking data described above, along with the immunocytochemistry results, suggest strongly that there is only one functional binding site for EGF in the adult testis and that this receptor is present in Sertoli and Leydig cells.