Transcriptional regulation of the lutropin/human choriogonadotropin receptor and three enzymes of steroidogenesis by growth factors in cultured pig Leydig cells

Influence of Immunocastration and Diet on Meat and Fat Quality of Heavy Female and Male Pigs

Two experiments were carried out; one with female pigs and the other with male pigs destined for Teruel dry-cured ham production, to evaluate the effect of immunocastration (entire gilts-EG vs. immunocastrated gilts-IG and surgically castrated males vs. immunocastrated males-IM) and diet (control vs. high energy vs. low crude protein and amino acids) on meat quality and fat composition. Fifteen meat samples and eight fat samples of each treatment were analyzed in both experiments. In the case of males, six fat samples per treatment were analyzed to determine boar taint. Immunocastration is a good strategy in gilts intended for dry-cured ham production because improves meat composition; however, in males, immunocastration impairs the results of pork chemical composition compared with surgical castration. The IG presented a lower polyunsaturated/saturated fatty acids ratio than EG, improving fat technological quality. Diets had little effect on pork or fat quality in gilts, but a high-energy level using oilseeds and a low-crude-protein and -amino-acids diet from 80 to 137 kg of body weight could be interesting in IM to maintain or increase fat consistency, respectively. Moreover, in general, immunocastration is effective in avoiding boar taint in males.

Immunolocalization of insulin-like growth factor-I (IGF-I) and its receptors (IGF-IR) in the equine epididymis

Insulin-like growth factor plays a paracrine/autocrine role in regulating testicular function in the stallion, but its presence in the equine epididymis remains unknown. The aim of this study was to test the hypothesis that insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-IR) are localized in the caput, corpus, and cauda of the epididymis in an age-dependent manner. Immediately after castration, epididymal tissue was fixed, paraffin-embedded, and processed for immunohistochemistry (IHC). Western blot was also performed using equine epididymal extracts to verify the specificity of the antibodies against IGF-I and IGF-IR. Immunolabeling of IGF-I was observed in the cytoplasm of principal and basal cells in the caput, corpus, and cauda at the pre-pubertal (3–7 months), pubertal (12–18 months), post-pubertal (2–4 years), and adult stages (4.5–8 years). Immunolabeling of IGF-IR was observed in the cytoplasm of principal cells in all regions of the epididymis in each age group. Immunolabeling of IGF-IR was also detected in the cytoplasm of basal cells from animals of all ages. Bands observed by Western blot corresponded to the molecular weights of IGF-I and IGF-IR, ~23 kDa and 95 kDa, respectively. These results suggest that IGF-I might function as an autocrine and/or paracrine factor during the development, maintenance and/or secretions of the stallion epididymis.

Basic fibroblast growth factor promotes stem Leydig cell development and inhibits LH-stimulated androgen production by regulating microRNA expression

Leydig cells are the primary source of testosterone in the testes, and their steroidogenic function is strictly controlled by the hypothalamus-pituitary-gonad axis. Emerging evidence has indicated that fibroblast growth factors play a role in regulating stem Leydig cell development and steroidogenesis, but little is known about the regulatory mechanism. Using a seminiferous tubule culture system, we demonstrated that basic fibroblast growth factor (bFGF) can promote stem Leydig cell proliferation and commitment toward differentiation in testosterone-producing Leydig cells. However, these promoting effects decreased with an increase in the bFGF dose. Previous studies have reported that bFGF inhibits luteinizing hormone (LH)-stimulated androgen production by downregulating the mRNA expression of steroidogenic genes in immature Leydig cells. However, the expression levels of 677 microRNAs did not change significantly during the LH-mediated process of testosterone synthesis. Five microRNAs (miR-29a, -29c, -142-3p, -451 and -335) were identified, and their expression in immature Leydig cells was regulated simultaneously by bFGF and LH. These results suggested that the inhibition of LH-stimulated androgen production may be modulated by a change in bFGF-mediated microRNA expression, which further impacts the signaling pathway of testosterone biosynthesis and steroidogenic gene expression.

Human conditions of insulin-like growth factor-I (IGF-I) deficiency

Insulin-like growth factor I (IGF-I) is a polypeptide hormone produced mainly by the liver in response to the endocrine GH stimulus, but it is also secreted by multiple tissues for autocrine/paracrine purposes. IGF-I is partly responsible for systemic GH activities although it possesses a wide number of own properties (anabolic, antioxidant, anti-inflammatory and cytoprotective actions). IGF-I is a closely regulated hormone. Consequently, its logical therapeutical applications seems to be limited to restore physiological circulating levels in order to recover the clinical consequences of IGF-I deficiency, conditions where, despite continuous discrepancies, IGF-I treatment has never been related to oncogenesis. Currently the best characterized conditions of IGF-I deficiency are Laron Syndrome, in children; liver cirrhosis, in adults; aging including age-related-cardiovascular and neurological diseases; and more recently, intrauterine growth restriction. The aim of this review is to summarize the increasing list of roles of IGF-I, both in physiological and pathological conditions, underlying that its potential therapeutical options seem to be limited to those proven states of local or systemic IGF-I deficiency as a replacement treatment, rather than increasing its level upper the normal range.

Growth hormone deficiency in the transition period: body composition and gonad function

Recombinant GH therapy is normally administered to GH-deficient children in order to achieve a satisfactory height - the main target during childhood and adolescence. However, the role of GH does not end once final height has been reached, but continues during the so-called transition period. In this phase of life, the body undergoes several changes, both physical and psychological, that culminate in adulthood. During this period, GH has a part in numerous metabolic functions. These include the lipid profile, where it increases HDL and reduces LDL, with the global effect of cardiovascular protection. It also has important effects on body composition (improved muscle strength and lean body mass and reduced body fat), the achievement of proper peak bone density, and gonad maturation. Retesting during the transition period, involving measurement of IGF-I plus a provocative test (insulin tolerance test or GHRH + arginine test), is thus necessary to establish any persistent GH deficiency requiring additional replacement therapy. The close cooperation of the medical professionals involved in the patient's transition from a pediatric to an adult endocrinologist is essential. The aim of this review is to point out the main aspects of GH treatment on body composition, metabolic and gonad functions in the transition period.

Inhibition of LH-stimulated androgen production in rat immature Leydig cells: Effects on nuclear receptor steroidogenic factor 1 by FGF2

Both fibroblast growth factor 2 (FGF2) and luteinizing hormone (LH) have been reported to regulate androgen production in Leydig cells in progenitor Leydig cells. The objective of the present study is to examine the regulation of androgen production in rat immature Leydig cells (ILCs). ILCs were isolated from 35-day-old rat testes and cultured in DMEM/F12 medium with LH (1 ng/ml) or FGF2 (10 ng/ml). 5alpha-Androstane-3alpha, 17beta-diol (3alpha-DIOL), the primary androgen in ILCs, and testosterone (T) were measured by Radioimmuno assay. The results showed the LH stimulated androgen production in ILCs, and FGF2 did not. However, FGF2 decreased the LH-stimulated androgen production. Real-time PCR and enzyme assay showed that FGF2 decreased levels of several steroidogenic enzymes, inhibited the expressions of steroidogenic acute regulatory (StAR) protein and steroidogenic factor 1 (Nr5a1) in LH-stimulated ILCs. FGF2-mediated inhibition of Nr5a1gene expression may be the mechanism through which FGF2 inhibits LH-stimulated androgen production.

Transcriptional regulation of steroidogenic genes: STARD1, CYP11A1 and HSD3B

Expression of the genes that mediate the first steps in steroidogenesis, the steroidogenic acute regulatory protein (STARD1), the cholesterol side-chain cleavage enzyme, cytochrome P450scc (CYP11A1) and 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (HSD3B), is tightly controlled by a battery of transcription factors in the adrenal cortex, the gonads and the placenta. These genes generally respond to the same hormones that stimulate steroid production through common pathways such as cAMP signaling and common actions on their promoters by proteins such as NR5A and GATA family members. However, there are distinct temporal, tissue and species-specific differences in expression between the genes that are defined by combinatorial regulation and unique promoter elements. This review will provide an overview of the hormonal and transcriptional regulation of the STARD1, CYP11A1 and specific steroidogenic HSD3B genes in the adrenal, testis, ovary and placenta and discuss the current knowledge regarding the key transcriptional factors involved.

Insulin-Like Growth Factor 1 Is Expressed in Mouse Developing Testis and Regulates Somatic Cell Proliferation

Testicular development occurs prenatally in mammals. The developmental underlying mechanism is only partially understood. The aim of the present investigation was to study the expression of the gene coding for insulin-like growth factor 1 ( Igf-1) and Igf-1 type 1 receptor ( Igf-1r) and their respective proteins in mouse Sertoli and Leydig cells at gestation day 12 (E12)–E18. Moreover, we sought to determine the effect of IGF-1 on the proliferation of both cell types and to establish the signal transduction mechanism involved in the IGF-1 pathway. Transcripts for the Igf-1 and Igf-1r genes were found in Sertoli and Leydig cells from E12–E18. Highest IGF-1 and IGF-Ir protein expression levels were found in both cell types at E18. Exogenous IGF-1 administration increased Sertoli and Leydig cell proliferation at E14–E18 in vitro. Inhibition of the pathway mitogen-activated extracellular signal-regulated protein kinase (MEK) 1/2 with UO126 diminished the proliferation of the Sertoli and Leydig cells in vitro. We propose that IGF-1 and IGF-1r regulate Sertoli and Leydig cell proliferation through the MEK/extracellular-signal-regulated kinase (ERK) 1/2 signal transduction pathway, leading to development and growth of the mouse embryonic testis.

Hypogonadism in male patients with cancer

BACKGROUND

Patients with cancer often develop anorexia, fatigue, and decreased muscle mass. These signs and symptoms are nonspecific, and they frequently occur in other conditions, including hypogonadism.

METHODS

The objectives of this study were 1) to measure testosterone levels in patients with cancer and 2) to examine the correlations between testosterone, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), insulin-like growth factor-1 (IGF-1), ghrelin levels, and appetite in patients with cancer patients and in a noncancer control group. This was designed as a cross-sectional study in the setting of a university-affiliated Veterans Affairs Medical Center. The study population included 31 male patients with cancer and 25 gender-matched noncancer controls of similar age. The variables total testosterone (TT), calculated free testosterone (cFT), calculated bioavailable testosterone (cBT), sex hormone-binding globulin (SHBG), luteinizing hormone (LH), TNF-alpha, IL-6, IGF-1, and active ghrelin were measured in fasting morning plasma samples. Appetite was measured according to a visual analog scale. The main outcome measures were cFT and cBT.

RESULTS

Cancer patients had mean TT levels similar to levels in the noncancer control group but significantly lower levels of cFT, cBT, IGF-1, and appetite. SHBG, LH, TNF-alpha, IL-6, and ghrelin levels were increased in patients with cancer compared with the control group. cFT and cBT levels were correlated inversely with IL-6 and ghrelin levels and were correlated directly with IGF-1 levels and appetite.

CONCLUSIONS

Patients with cancer had lower levels of biologically active testosterone. TT was not adequate for the evaluation of hypogonadism, because SHBG levels were increased. A reliable measurement of FT and/or BT should be used. LH was elevated in the patients with cancer, indicating that low FT levels were caused by primary testicular dysfunction. The authors postulated that high IL-6 or ghrelin levels inhibit testosterone synthesis, although a secondary effect at the hypothalamic-pituitary levels cannot be excluded.

Molecular Mechanisms of Insulin-like Growth Factor-I Mediated Regulation of the Steroidogenic Acute Regulatory Protein in Mouse Leydig Cells

Growth factors are known to play diverse roles in steroidogenesis, a process regulated by the mitochondrial steroidogenic acute regulatory (StAR) protein. The mechanism of action of one such growth factor, IGF-I, was investigated in mouse Leydig tumor (mLTC-1) cells to determine its potential role in the regulation of StAR expression. mLTC-1 cells treated with IGF-I demonstrated temporal and concentration-dependent increases in StAR expression and steroid synthesis. However, IGF-I had no effect on cytochrome P450 side-chain cleavage or 3beta-hydroxysteroid dehydrogenase protein levels. IGF-I was capable of augmenting N,O'-dibutyrl-cAMP-stimulated steroidogenic responsiveness in these cells. The steroidogenic potential of IGF-I was also confirmed in primary cultures of isolated mouse Leydig cells. IGF-I increased phosphorylation of ERK1/2, an event inhibited by the MAPK/ERK inhibitors, PD98059 and U0126. Interestingly, inhibition of ERK activity enhanced IGF-I-mediated StAR protein expression, but phosphorylation of StAR was undetectable, an observation in contrast to that seen with N,O'-dibutyrl-cAMP signaling. Further studies demonstrated that these events were tightly correlated with the expression of dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene 1 and scavenger receptor class B type 1. Whereas both protein kinase A and protein kinase C signaling were involved in the IGF-I-mediated steroidogenic response, the majority of the effects of IGF-I were found to be mediated by the protein kinase C pathway. Transcriptional activation of the StAR gene by IGF-I was influenced by several transcription factors, its up-regulation being dependent on phosphorylation of the cAMP response element-binding protein (CREB) and the activator protein 1 family member, c-Jun. Conversely, StAR gene transcription was markedly inhibited by expression of nonphosphorylatable CREB (Ser(133)Ala), dominant negative A-CREB, and dominant negative c-Jun (TAM-67) mutants. Collectively, the present studies identify molecular events in IGF-I signaling that may influence testicular growth, development, and the Leydig cell steroidogenic machinery through autocrine/paracrine regulation.

Expression and localization of growth factors and their receptors in the mammalian testis. Part I: Fibroblast growth factors and insulin-like growth factors

It is now well established that normal development and function of testis are mediated by endocrine and paracrine pathways including hormones, growth factors and cytokines as well as by direct cell-to-cell contacts depending on tight, adhering and gap junctions. In the last two 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. Interestingly, most of these peptides are expressed not only in the adult mammalian testis during spermatogenesis but also during testicular morphogenesis in prenatal and postnatal life. Our study was launched to provide an overview of the expression, localization, and putative physiological roles of growth factors and their receptors in the mammalian testis. The growth factors considered in this part of our review are fibroblast growth factors and insulin-like growth factors. These factors are found in testicular cells in prenatal, postnatal, and adult animals and are implicated in the regulation of important testicular activities including testicular cord morphogenesis, modulation of testicular hormone secretion and control of spermatogenesis.

A comparison of the effects of equine luteinizing hormone (eLH), equine growth hormone (eGH) and human recombinant insulin-like growth factor (hrIGF-I) on steroid production in cultured equine Leydig cells during sexual maturation

There are several hormones and local testicular factors involved in the initiation and control of steroidogenesis and spermatogenesis during puberty. GH and its mediator, IGF-I, increase substantially during puberty, and in addition to LH, these growth-promoting hormones can have direct effects upon testicular function. The objective of this work was to investigate the effects of eLH, eGH and hrIGF-I upon Leydig cells derived from testes of colts and stallions representing different stages of development. Testes were obtained from 48 light horse colts and stallions at the time of routine castration, horses were categorized according to age group (prepubertal, pubertal and postpubertal) and a Leydig cell enriched preparation was utilized for cell culture. Cells derived from all 48 horses were treated with doses of eLH, and a subset of 21 horses received doses of eGH and hrIGF-I. Cells were plated at a concentration of 1 x 10(6) cells/ml and incubated for 24 h at 32 degrees C. Production of testosterone and estradiol was measured by validated RIA. Leydig cells from prepubertal colts secreted greater basal amounts of testosterone but lesser basal amounts of estradiol compared with the other age groups (p < 0.001). Pubertal stallions exhibited the greatest relative response to eLH (p < 0.05). Neither eGH nor hrIGF-I elicited a steroidogenic response over baseline concentrations in any of the three age groups.

The Consequences of Altered Somatotropic System on Reproduction1

Although the primary control of gonadotropin secretion is by the hypothalamic GnRH and the gonadal function is controlled by the pituitary gonadotropins and prolactin, the emerging evidence suggests a vital role of the somatotropic axis, growth hormone (GH), and insulin-like growth factor-I (IGF-I) in the control of the pituitary and gonadal functions. It has been shown that GH deficiency, GH resistance, and experimental alterations in IGF-I secretion modify folliculogenesis, ovarian maturation, ovulation, and pregnancy, and in the male, GH/IGF-I plays an important role in spermatogenesis and the Leydig cell function. The primary focus of this review is to examine the role of GH/ IGF-I on the onset of puberty, fertility, pituitary, and gonadal endocrine functions. A number of studies have revealed that fertility is affected in GH-deficient dwarf and in IGF-I gene-ablated mice, possibly due to subnormal function of either the pituitary gland or the gonads. In the female GH receptor gene knockout (GHR-KO) mice, there was impairment in follicular development, ovulation rate, sexual maturation, production of and responsiveness to pheromonal signals, and the corpus luteum function. In IGF-I-deficient male GHR-KO mice, puberty is delayed, spermatogenesis is affected, and neuroendocrine-gonadal function is attenuated. Similarly, in some of the human Laron syndrome patients, puberty is delayed due to GH resistance. These data suggest that, in addition to GnRH and gonadotropins, GH/IGF-I influences the pituitary and gonadal functions in animals and humans.

Expression and regulation of luteinizing hormone/human chorionic gonadotropin receptors in ovarian cancer and its correlation to human chorionic gonadotropin-doxorubicin sensitivity

OBJECTIVE

Ovarian cancer cell lines and tissues express gonadotropin receptors. Conjugation of cytostatics to ligands of these receptors may increase the specificity of cytotoxic drugs.

STUDY DESIGN

Toxicity of doxorubicin-human chorionic gonadotropin conjugates was determined in 4 ovarian cancer cell lines. Expression and regulation of luteinizing hormone/human chorionic gonadotropin receptors were analyzed before and after treatment with human chorionic gonadotropin, epidermal growth factor, and 8-bromo-cyclic adenosine monophosphate with a nested reverse transcriptase-polymerase chain reaction approach.

RESULTS

Toxicity of human chorionic gonadotropin-doxorubicin conjugates was increased compared with unconjugated doxorubicin in OVCAR-3 cells. However, drug conjugates failed to demonstrate increased toxicity in other cell lines, especially after preincubation with human chorionic gonadotropin. All cell lines expressed luteinizing hormone/human chorionic gonadotropin receptors. Receptor expression in OVCAR-3 cells was not effected by human chorionic gonadotropin, endothelial growth factor, or 8-bromo-cyclic adenosine monophosphate treatment. In other cell lines, receptor expression was down-regulated by these agents.

CONCLUSION

Cytotoxic activity of doxorubicin was increased specifically by conjugation to human chorionic gonadotropin. However, the regulation of luteinizing hormone/human chorionic gonadotropin receptor expression and other compounds may reduce the drug-uptake of the conjugates.

Retinoid-Sensitive Steps in Steroidogenesis in Fetal and Neonatal Rat Testes: In Vitro and In Vivo Studies

Retinoic acid (RA) was recently shown to modify testosterone secretion of the fetal testis in vitro. We characterized this effect by culturing rat testes explanted at various ages, from Fetal Day 14.5 to Postnatal Day 3. In basal medium, RA inhibited, in a dose-dependent manner, both basal and acute LH-stimulated testosterone secretion by testes explanted on Fetal Days 14.5, 15.5, and 16.5. It had no effect on testes from older animals. The negative effect of RA did not result from a diminution in the number of Leydig cells but from a decrease in P450c17 mRNA levels and in LH-stimulated cAMP production. However, the RA-induced decrease in P450C17 mRNA levels was also observed with neonatal testes, suggesting that this enzymatic step is no longer rate limiting at this developmental stage. To study the physiological relevance of RA effects, we used fetuses and neonates issued from mothers fed a vitamin A-deficient (VAD) diet, resulting in a threefold decrease of plasma retinol concentration. On Fetal Day 18.5 and on Posnatal Day 3, testosterone secretion by the testis ex vivo was significantly increased in VAD animals. This shows that the endogenous retinol inhibits differentiation and/or function of fetal Leydig cells before Fetal Day 18.5 and is required for the normal regression of fetal Leydig cell function that occurs after Fetal Day 18.5. In conclusion, our results show that retinoids play a negative role on the steroidogenic activity during the differentiation of rat fetal Leydig cells.

Reproductive abnormalities in human insulin-like growth factor-binding protein-1 transgenic male mice

Adult transgenic mice overexpressing human insulin-like growth factor-binding protein-1 in the liver present reproductive abnormalities in both sexes. In the present work, we have investigated the mechanisms responsible for limiting breeding capacity in these transgenic male mice. Homozygous adult transgenic male mice (3-6 months old) exhibited irregular copulatory behavior and a reduction of the number of pregnancies per female as well as of litter size per pregnancy. Genital tract weight, more specifically epididymal and seminal vesicle weights, were reduced by 45% in homozygous transgenic vs. nontransgenic mice. Homozygous transgenic mice exhibited a 30% reduction of the length of seminiferous tubules (P = 0.007), a 30% decrease in daily sperm production per testis (P = 0.019), and a 50% decrease in the number of spermatozoa in testis (P = 0.037), associated with morphological abnormalities of the sperm heads leading to an approximately 50% reduction of fertilized two-cell eggs (P = 0.002) and of implanted embryos on d 5.5 after mating (P = 0.004). The round spermatids also appeared altered in their morphology. In addition, Leydig cells in homozygous transgenic mice exhibited an altered appearance, with a 1.8-fold increase in lipid droplets in their cytoplasm (P < 0.001). Moreover, the concentration of 3beta-hydroxysteroid dehydrogenase was 66% lower in testis from transgenics compared with those from normal mice (P = 0.01), leading to a tendency toward lower plasma testosterone levels (P = 0.1). Interestingly, LH concentrations were increased by 40% in transgenic pituitary extracts (P = 0.02), and basal LH secretion by pituitary explants in vitro was increased by 60% in homozygous transgenic vs. normal mice (P = 0.04), suggesting an alteration of LH pulsatile secretion in vivo. In conclusion, these data suggest that the breeding impairment of human insulin-like growth factor-binding protein-1 transgenic males is due at least in part to an alteration of the process of spermatogenesis, leading to a diminution of sperm production and of its quality. Minor impairment of steroidogenesis may also contribute to the reduced reproductive capacity of these animals. Our observations are consistent with the idea that normal spermatogenesis and perhaps also steroidogenesis are dependent on the actions of sufficient concentrations of unbound IGF-I.

Development of Leydig Cells in the Insulin-Like Growth Factor-I (IGF-I) Knockout Mouse: Effects of IGF-I Replacement and Gonadotropic Stimulation1

Targeted gene deletion of insulin-like growth factor-I (IGF-I) results in diminished numbers of Leydig cells (LCs) and lower circulating testosterone (T) levels in adult males. The impact of endogenous IGF-I withdrawal on proliferation (labeling index, LI) and differentiation of LCs was investigated, testing for restorative effects of IGF-I replacement and/or LH stimulation. With IGF-I replacement in mutant mice, LIs increased more than 200% (P < 0.05). LC numbers were also increased by 200%, whereas the numbers of intermediate cell progenitors (PLCs) were unchanged compared to mutant vehicle controls. LIs of PLCs in wild-type males increased by 200% after LH stimulation, and LC numbers increased by 50% compared to vehicle-treated controls (P < 0.05). In contrast, there was no effect of LH on LI in mutant mice, but LC numbers still increased by 30% (P < 0.05). Additive effects on LI and cell numbers were observed in response to IGF-I plus LH in mutants, implying that the two hormones use separate signaling pathways. Serum T and LH levels in wild-type and mutant males were equivalent. Exogenous LH increased T production 8-fold in wild-type males (P < 0.01). In mutant mice, neither LH stimulation nor IGF-I alone affected serum T levels, but IGF-I plus LH stimulation increased serum T 2-fold (P < 0.05). These data support the conclusions that 1) IGF-I is a critical autocrine and/or paracrine factor in the control of adult LC numbers and function; and 2) LH is not a direct mitogenic factor for LCs, and acts in part through IGF-I to stimulate proliferative activity.

Insulin drives transcriptional activity of the CYP17 gene in primary cultures of swine theca cells

Insulin stimulates androgen biosynthesis and the accumulation of CYP17 mRNA and heterogeneous nuclear (hn) RNA in primary cultures of immature swine theca cells. To further assess insulinomimetic transcriptional control, we subcloned 1.007 kilobases (kb) of the 5'-upstream region of the CYP17 gene (-976 to +31 base pairs [bp] to the transcriptional start site) into a firefly-luciferase reporter construct. Insulin drove transcriptional activity of this probe in a time- and dose-dependent fashion, with maximal stimulation of 2.7- to 3.2-fold after insulin exposure (100 ng/ml) for 6 h. Progressive deletional constructs -839, -473, -174, and -75/+31 bp delineated expected reduction in responsiveness, except paradoxical gain of basal CYP17 promoter activity by the -473/+31-bp sequence. The latter suggests a possible intervening inhibitory sequence. Elimination of all sequences 5'-upstream to -174 bp markedly reduced basal transcriptional activity and abolished insulin action. Point mutation of a presumptive Sp1-like element located within -193/-180 bp inhibited basal and insulin-stimulated luciferase activity of the full-length promoter fragment by 40% and 67%, respectively. Disruption of a contiguous presumptive AP-2 site produced a comparable outcome. Combined mutation of the Sp1 and AP-2-like elements eliminated basal and insulin-potentiated CYP17 promoter activity. By Western analysis, insulin augmented cognate receptor phosphoprotein concentrations by 31-fold within 10 min. Chemical inhibitors of MEK-activated ERK1/2 attenuated insulin-enhanced CYP17 transcriptional activity by 76-80%. In summary, insulin drives transcriptional activity of a 5'-upstream regulatory sequence (-976 to +31 bp) of the swine CYP17 gene in primary cultures of theca cells, under a minimal requirement for combined activity of proximal (-193/180 bp) Sp1 and AP-2-like elements.

Insulin-like growth factor I (IGF-I) regulates endocrine activity of the embryonic testis in the mouse

Insulin-like growth factor I (IGF-I) is important for gonadal and reproductive functions in mammals, although the physiological role of this growth factor during gonadal development in rodents remains largely unknown. Here, we examined the steady-state levels of IGF-I mRNA by the reverse transcriptase polymerase chain reaction (RT-PCR). IGF-I protein expression was also detected by Western blot. The effect of IGF-I as promoter of 17alpha-hydroxylase/C17-20 lyase and 17beta-hydroxysteroid dehydrogenase enzyme activity in vitro was evaluated by radioimmunoassay. Onset of IGF-I gene expression was on day E10 (urogenital ridge stage). IGF-I mRNA expression was markedly reduced on days E12 and E13 (testicular differentiation stage). IGF-I transcripts increased on day E14 and their transcription levels were maintained throughout the stages analyzed. Several IGF-I protein bands of 31-100 kDa were observed. Culture experiments demonstrated that 17alpha-hydroxyprogesterone and testosterone (T) secretion levels increased in the presence of IGF-I on days E11-E17. Additive effects of IGF-I plus (Bu)2cAMP were also seen during testicular development. It is proposed that IGF-I regulates the expression of key steroidogenic enzymes important for endocrine activity of the testis during prenatal development leading to establishment of the male phenotype and fertility.

Src tyrosine kinase-induced loss of luteinizing hormone responsiveness is via a Ras-dependent, phosphatidylinositol-3-kinase independent pathway

Gonadotropins stimulate gonadal cell steroid secretion primarily through activation of a cAMP-protein kinase A signal transduction pathway. Various growth factors have been shown to inhibit gonadotropin-stimulated steroidogenesis, however, the intracellular signaling cascades involved in growth factor inhibition have not been characterized. The present study investigated whether Src tyrosine kinase, a nonreceptor tyrosine kinase activated in response to growth factor stimulation and previously shown to inhibit LH-stimulated progesterone secretion, acts via activation of Ras stimulated pathways, phosphatidylinositol-3-kinase (PI3-kinase) stimulated pathways, or both in MA10 Leydig cells. Direct activation of Src in MA10 cells that express a temperature sensitive Src was associated with an increase in GTP-bound Ras, indicating increased Ras activity in response to Src activation. Direct activation of Ras by way of expression of a constitutively active Ras (Ras+) was associated with a decrease in LH responsiveness. Coexpression of a dominant negative Src, which by itself increases LH responsiveness in MA10 cells, had no effect on Ras+ inhibition on LH responsiveness, further demonstrating that Src is upstream of Ras. In addition, MA10(Ras+) cells were relatively unresponsive to cholera toxin or 8-bromo cAMP, indicating the effects of Ras are independent of cAMP generation. Wortmannin, a PI3-kinase inhibitor, did not restore LH responsiveness to cells expressing activated Src or constitutively active Ras. These results demonstrate that Src activates a Ras pathway in MA10 Leydig cells, and that activation of Ras is associated with a loss of LH responsiveness that is independent of PI3-kinase.

Endocrine and paracrine control of sperm production in stallions

The specific nature and relative contribution of the major hormones involved in regulation of reproductive function of the stallion are not well defined nor have paracrine or autocrine factors been identified. Over the last 12 years, our laboratory has been engaged in characterizing the hypothalamic-pituitary-testicular axis (HPT) in stallions. A number of endocrine factors and mechanisms important for normal reproductive function have been investigated. Studies investigating poor fertility in stallions suggest that a closer look at the testicular level is warranted. For a complete understanding of intratesticular control mechanisms including cell-to-cell interactions in the stallion, studies on the actions of paracrine/autocrine factors such as growth factors, inhibin, activin, and oxytocin are needed. In other species, paracrine/autocrine systems appear to be important in modulating endocrine control of testicular function and spermatogenesis.

Energy balance and cancer: the role of insulin and insulin-like growth factor-I

Recent theories propose that a Western lifestyle may increase cancer risk through alterations in the metabolism of insulin and insulin-like growth factors (IGF: McKeown-Eyssen, 1994; Giovannucci, 1995; Kaaks, 19%; Werner & LeRoith, 1996). Insulin regulates energy metabolism, and increases the bioactivity of IGF-I, by enhancing its synthesis. and by decreasing several of its binding proteins (IGFBP; IGFBP-1 and -2). Insulin and IGF-I both stimulate anabolic processes as a function of available energy and elementary substrates (e.g. amino acids). The anabolic signals by insulin or IGF-I can promote tumour development by inhibiting apoptosis, and by stimulating cell proliferation. Furthermore, both insulin and IGF-I stimulate the synthesis of sex steroids, and inhibit the synthesis of sex hormone-binding globulin (SFIBG), a binding protein that regulates the bioavailability of circulating sex steroids to tissues. The present paper reviews epidemiological findings relating the risk of cancers of the colo-rectum, pancreas, breast, endometrium and prostate to body size (obesity, height) and physical activity, and discusses the relationships between obesity and physical activity and plasma levels of insulin, IGF-I and IGFBP. Subsequent sections review epidemiological findings relating cancer risk to indices of chronic hyperinsulinaemia, and to plasma levels of IGF-I and IGFBP. Conclusions are that chronic hyperinsulinaemia may be a cause of cancers of the colon, pancreas and endometrium, and also possibly of the breast. On the other hand, elevated plasma IGF-I, as total concentrations or relative to levels of IGFBP-3, appears to be related to an increased risk of prostate cancer, breast cancer in young women, and possibly cob-rectal cancer. For cancers of the endometrium, breast and prostate, these findings are discussed in the context of relationships between insulin and IGF-I and levels of bioavailable sex steroids.

Regulation by adrenocorticotropin (ACTH), angiotensin II, transforming growth factor-beta, and insulin-like growth factor I of bovine adrenal cell steroidogenic capacity and expression of ACTH receptor, steroidogenic acute regulatory protein, cytochrome P450c17, and 3beta-hydroxysteroid dehydrogenase

The purpose of this study was to evaluate the time-course effect of a 36-h treatment with ACTH (10(-8) M), transforming growth factor-beta1 (TGFbeta1; 10(-10) M), angiotensin II (AngII; 10 (-7) M), and insulin-like growth factor I (IGF-I; 10(-8) M) on the steroidogenic capacity of bovine adrenocortical cells (BAC) and on messenger RNA (mRNA) levels of ACTH receptor, cytochrome P450c17, 3beta-hydroxysteroid dehydrogenase (3betaHSD), steroidogenic acute regulatory protein (StAR), and StAR protein. ACTH and IGF-I enhanced, in a time-dependent manner, the acute 2-h ACTH-induced cortisol production, whereas TGFbeta 1 and AngII markedly reduced it. ACTH, IGF-I, and AngII increased ACTH receptor mRNA, but the opposite was observed after TGFbeta1 treatment. ACTH and IGF-I increased P450c17 and 3betaHSD mRNAs, whereas AngII and TGFbeta1 had the opposite effects. However, the effects of the four peptides on ACTH-induced cortisol production appeared before any significant alterations of the mRNA levels occurred. The most marked and rapid effect of the four peptides was on StAR mRNA. The stimulatory effect of ACTH was seen within 1.5 h, peaked at 4-6 h, and declined thereafter, but at the end of the 36-h pretreatment, the levels of StAR mRNA and protein were higher than those in control cells. IGF-I also enhanced StAR mRNA levels within 1.5 h, and these levels remained fairly constant. The effects of AngII on StAR mRNA expression were biphasic, with a peak within 1.5-3 h, followed by a rapid decline to almost undetectable levels of both mRNA and protein. TGFbeta1 had no significant effect during the first 3 h, but thereafter StAR mRNA declined, and at the end of the experiment the StAR mRNA and protein were almost undetectable. Similar results were observed when cells were treated with ACTH plus TGFbeta1. A 2-h acute ACTH stimulation at the end of the 36-h pretreatment caused a higher increase in StAR mRNA and protein in ACTH- or IGF-I-pretreated cells than in control cells, which, in turn, had higher levels than cells pretreated with TGFbeta1, ACTH plus TGFbeta1, or AngII. These results and the fact that the stimulatory (IGF-I) or inhibitory (AngII and TGFbeta1) effects on ACTH-induced cortisol production were more pronounced than those on the ability of cells to transform pregnenolone into cortisol strongly suggest that regulation of StAR expression is one of the main factors, but not the only one, involved in the positive (IGF-I) or negative (TGFbeta1 and AngII) regulation of BAC for ACTH steroidogenic responsiveness. A high correlation between steady state mRNA level and acute ACTH-induced cortisol production favors this conclusion.

The insulin-like growth factor (IGF) system and gonadotropin regulation: actions and interactions

Insulin-like growth factors (IGF) are polypeptides that regulate growth, differentiation and survival in a multitude of cells and tissues. The IGF system consists of ligands, receptors, binding proteins and binding protein proteases. The influence of the IGF system on reproductive parameters, specifically gonadotropin release and interactions between the IGF system and other effectors of gonadotropin release will be examined in this review.

Growth factor modulation of steroidogenic acute regulatory protein and luteinization in the pig ovary

In vivo and in vitro luteinization were investigated in the porcine ovary, with emphasis on expression of steroidogenic acute regulatory protein (StAR). StAR mRNA and protein as well as cytochrome P450 side-chain cleavage mRNA (P450scc) increased during the luteal phase in the corpus luteum (CL) and were absent in regressed CL. Cytochrome P450 aromatase mRNA (P450arom) was not detectable at any time in CL. In vitro luteinization of granulosa cells occurred over 96 h in culture, during which P450arom mRNA was present at 1 h after cell isolation but not detectable at 6 h; and P450scc and StAR mRNAs were first detectable at 6 h and 48 h, respectively. Incubation of cultures with insulin-like growth factor I (IGF-I, 10 ng/ml), dibutyryl cAMP (cAMP, 300 microM), or their combination, induced measurable StAR mRNA at 24 h (p < 0.05), increased progesterone accumulation at 48 h, and elevated both StAR and P450scc expression through 96 h. Incubation of luteinized granulosa cells with epidermal growth factor (EGF, 10 nM) changed their phenotype from epithelioid to fibroblastic, eliminated steady-state StAR expression, and interfered with cAMP induction of StAR mRNA and progesterone accumulation. EGF had little apparent effect on P450scc mRNA abundance. It is concluded that StAR expression characterizes luteinization, and early luteinization is induced by cAMP and IGF-I in vitro. Further, EGF induces a morphological and functional phenotype that appears similar to an earlier stage of granulosa cell function.

Autocrine regulation of Leydig cell differentiated functions by insulin-like growth factor I and transforming growth factor beta

The expression and the maintenance of specific differentiated function of Leydig cells are regulated not only by gonadotropin but by locally produced factors, which may act as autocrine regulators. Many factors, in particular growth factors, have been postulated to have such a type of effect on testicular cells, but very few fulfilled the three criteria required to establish a paracrine/autocrine role: (a) presence of receptors and biological action on local cells; (b) local secretion regulated by physiological signals; and (c) blockade of the factor or its receptors must modify the function of local cells. In the present work we demonstrate that two factors, insulin-like growth factor 1 (IGF-I) and transforming growth factor beta1 (TGFbeta1) fulfilled the three criteria: (a) IGF-I stimulates the transcription of the genes encoding Leydig cell differentiated function, leading to an enhanced steroidogenic responsiveness to LH/hCG; (b) Leydig cells (LC) express and secrete IGF-I and this secretion is enhanced by hCG; and (c) incubation of LC with IgG anti-IGF-I, but not with IgG-control, markedly reduced the steroidogenic responsiveness to LH/hCG. In contrast to IGF-I, TGFbeta is a potent inhibitor of LC differentiated function. Moreover, LC express TGFbeta1 mRNA and secrete this peptide. To prove that the locally produced TGFbeta has an autocrine role, LC were transfected with 10 microM of an antisense oligonucleotide (AON) complementary to the translation initiation region of TGFbeta1 mRNA. Transfection with AON but not with sense deoxynucleotide induces a complete disappearance of TGFbeta immunoreactivity in LC and an enhanced hCG-induced testosterone production by LC. This increased steroidogenic responsiveness was associated with a significant enhancement of both LH/hCG receptor mRNA and P450c17 mRNA. Taken together, the above results show that both factors play an autocrine role, although opposite, on Leydig cell function.

Induction of oxytocin receptor gene expression in rabbit amnion cells

Oxytocin (OT)-stimulated PGE2 release by rabbit amnion is enhanced by the up-regulation of oxytocin receptors (OTR), which increase about 200-fold at the end of pregnancy. As recent studies have shown that PGs are essential for parturition, the rise in amnion OTR and associated PGE2 synthesis are probably essential for labor initiation. The present work was directed toward understanding the mechanisms of OTR up-regulation. Levels of agents that stimulate adenylyl cyclase activity and cortisol are increased in amniotic fluid at the end of pregnancy. Addition of either forskolin or cortisol to cultured amnion cells caused an increase in OTR ligand-binding sites and steady state OTR messenger RNA (mRNA) levels. Forskolin treatment elevated OTR mRNA levels rapidly, but transiently, whereas cortisol's effects were slower and sustained. Actinomycin or cycloheximide, added 3 h after forskolin, led to a sustained elevation in OTR mRNA levels, suggesting that forskolin increases the activities of OTR mRNA-destabilizing factors along with increasing OTR mRNA concentration. Cortisol did not appear to affect OTR mRNA stability. Measurement of OTR mRNA transcription rates showed that forskolin's effects were maximal within 1 h of treatment. In contrast, cortisol-induced transcription was not apparent until 8 h. The effects of forskolin and cortisol on OTR gene transcription were synergistic. Thus, the increase in OTR mRNA levels occurring after either forskolin or cortisol treatments is the result of induction of OTR gene expression, but the effects of the two agents appear to occur at separate sites.

Low dihydrotestosterone and weight loss in the AIDS wasting syndrome

24 consecutive AIDS patients with wasting, and who had never received anabolic therapies, were evaluated to determine their profile of sex hormones and whether transformation of testosterone (T) to the nuclear androgen, dihydrotestosterone (DHT), was impaired. Eleven (46%) patients had normal testosterone and DHT (group I), 10 (42%) had normal testosterone but low DHT (group II), and 3 (12%) had low testosterone and low DHT (group III). Age, prior opportunistic complications, symptoms, serum albumin, hemoglobin levels, and CD4 lymphocyte counts were similar in the groups. DHT was significantly lower (22.2 +/- 6.8 microg/dl) in group II compared with group I (50.8 +/- 15.3 microg/dl). The ratio of T/DHT, a measure of the conversion of testosterone to DHT, in group I was 15.1 +/- 3.5, which was within the range for eugonadal young men. In group II, the ratio was 22.3 +/- 1.5, indicating a defect in generation of DHT. Patients in group II had lost 9.2 +/- 3.5 kg compared with 5.6 +/- 2.6 kg in group I (p = .015). Thus, a syndrome of low DHT with normal testosterone was associated with significantly greater weight loss than in patients with normal testosterone and DHT. Further studies are needed to clarify whether low DHT is a result of AIDS wasting or is causally related to weight loss and whether androgen therapy in the form of DHT could reverse some of the metabolic changes associated with AIDS wasting.

Expression and effect of insulin-like growth factor I on rat fetal Leydig cell function and differentiation

Insulin like growth factor I (IGF-I) is believed to be a potent para/autocrine stimulator of Leydig cell function in adult testis. We investigated whether IGF-I is also an intratesticular regulator of fetal Leydig cell function by measuring its production in the fetal testis and its ability to affect testicular steroidogenesis during fetal development. Northern blot analysis revealed one major IGF-I transcript of 7-7.5 kb and two minor transcripts of 3.8 and 1.8 kb in 20.5 day fetal testis. IGF-I was detected by RIA in 16.5 fetal day testes, and the amounts of IGF-I secreted by 16.5 and 20.5 fetal day testes in vitro were much greater than the amounts contained in the testes, indicating active synthesis in culture. The secretion of IGF-I by the fetal testis in vitro was increased with testicular age and time in culture. It was not modified by gonadotropins or (Bu)2cAMP. Testosterone secretion by fetal testes explanted 13.5, 16.5, 18.5, and 20.5 days after conception and cultured in the presence or absence of 100 ng/ml LH for 3 days was not affected by the addition of 50 ng/ml IGF-I to the medium. In contrast, the addition of IGF-I to dispersed fetal testicular cells cultured for 3 days in the presence or absence of LH increased the number of Leydig cells identified by a positive cytochemical reaction for 3beta-hydroxysteroid dehydrogenase (3betaHSD). This was more pronounced with cells from 16.5- day-old fetuses (stage when the fetal Leydig cells are differentiating in vivo) than with 20.5-day-old fetuses cells (stage when the number and the function of fetal Leydig cells are stable or decreasing). It results from both an increased differentiation of mesenchymal cells in fetal Leydig cells and an increase in the mitotic index of the fetal Leydig cells, as inferred from the small increase in the percentage of bromodeoxyuridine/3betaHSD-positive cells. Both LH and IGF-I increased significantly testosterone production by day 16.5 cells. In the presence of LH, a high amount of testosterone was produced per 3betaHSD-positive cell; IGF-I further increased this production. This effect was not observed with day 20.5 cells. The amounts of testosterone produced per 3betaHSD-positive cell cultured in the presence of both LH and IGF-I were more than additive. Like IGF-I, insulin (50 ng/ml) increased testosterone secretion per 3betaHSD-positive cells in cultures of day 16.5 cells, but not in those of day 20.5, cells. Lastly, IGF-I also increased the steroidogenic activity of each Leydig cell in cultures containing (Bu)2cAMP, but its effects were weaker than those observed in the presence of LH. This suggests that IGF-I has sites of action both upstream and downstream cAMP generation. These results suggest that IGF-I acts as paracrine/autocrine factor in the differentiation and activity of fetal Leydig cells.

Recent advances in clinical/molecular andrology

During the last decade there were extensive investigations in clinical and molecular andrology with emphasis on assisted reproduction, micromanipulation techniques of gametes, sperm/egg interaction, male contraception, diabetes mellitus, varicocele, andropause versus menopause, sexual dysfunction, associated hypertension/stress, prostatic carcinoma and molecular parameters of male reproduction. Sperm hyperactivation is a required step in capacitation sequence. Sperm motility is measured by videotape to evaluate the Straight Line Velocity (microm/s) (VSLI). Fertilization/embryonic development results from single sperm transfer (S-MIST) and multiple sperm transfer. Fertilization/embryo development is achieved by injection of immotile sperm into the perivitelline space. To assess sperm viability, a supravital stain suitable for use in combination with immunofluorescent assay, Hoeschst 33258, is used. The dye fluoresces with an intense blue when bound to DNA. To assess sperm plasma membrane integrity, a hypo-osmotic swelling test (HOST) is performed, using fluoresceinated D-mannose enriched albumin (FITC-DMA). The ability of sperm to swell under hypo-osmotic conditions indicates an intact membrane. A human protein, C-peptide, thought to be a useless byproduct of insulin may protect against devastating heart and nerve damage that diabetes causes. Human diabetics may benefit from the substance. Over 15 million Americans have diabetes, in which blood sugar levels rise out of control. There are two types of diabetics: Type I diabetics produce no insulin, the hormone that regulates blood sugar. Type II diabetics are unable to use their insulin properly. Diabetics are at great risk of heart disease and nerve damage, as arteries throughout the body leak and nerve-cell impulses fail. C-peptide is a byproduct of insulin production; it can be produced by the body or synthetically. Production of this protein is not induced by insulin, so diabetics who take insulin do not get C-peptide with it. Varicocele occurs unilaterally on the left side in 78% to 93% of men. Typically the presence of a varicocele is associated with an abnormal semen analysis (sperm density and morphology) and a decreased testicular volume on the affected side. Impaired sperm motility occurs in 89.5% of all varicocele patients. Varicocele ligation improves semen parameters in two thirds of patients. A few studies on andropause included sexual dysfunction, hormonal changes, medical/psychological correlates of impotence, ostenopenia/osteoporosis and bone loss; indices of bone remodeling, testosterone supplementation, androgen, negative feedback and hypothalamo-pituitary-testicular axis. Prostatic cancer is the second leading cause of cancer death for men between the ages of 60 and 80. Early detection involves a simple blood test for prostate specific antigen (PSA). Regular screening and early detection are essential. This is an important test because a high antigen count can be the only symptom. Since no screening is 100% accurate, physicians recommend both a PSA blood test and a physical examination. Although heredity plays a major role in whether a man will develop prostate cancer, men who lead healthy lives can dramatically reduce their chances of cancer: low-fat diet, eating plenty of fruits and vegetables and not smoking. Recent advances in molecular andrology include peptide hormone binding proteins; gonadotropin-releasing hormone (GnRH) agonists/antagonists analog; gonadotropins/their receptors; growth factors/reproduction; peptides as intratesticular regulators; molecular cloning of reproductive proteins/peptides. Gene cloning is applied for characterization/expression of genes coding. The interaction of gp120 with CD4 receptor plays a role in syncytium formation, apoptosis and CD4 cell deletion in human immunodeficiency virus (HIV) infection. The recombinant V3 peptide of fragment 307-330 of HIV-1 can induce sperm head agglutination. The generation process of react

Impact of aging and diabetes mellitus on the expression of the proliferating cell nuclear antigen in rat testicular tissue

This study evaluated the expression of proliferating cell nuclear antigen (PCNA), which is one of the important markers of cell proliferation, in testicular tissue with aging and progress of diabetes mellitus (DM). OLETF rats were used as animal models for non-insulin-dependent DM. They were 12, 30, 50, and 70 weeks old. The controls were age-matched nondiabetic LEIO rats. Testes were taken from all the rats and paraffin-embedded sections were cut and stained with PC 10 monoclonal AB (x50). Labeled cells were assessed in randomly selected fields. Labeling index (LI) for each stage of spermatogenesis was estimated and total LI for each specimen was calculated. In control rats, the 12-week-old animals showed the highest PCNA-LI. The indexes started to decrease in other older animals, with an increase in the number of suppressed stages as the animals aged, leading to significant differences among groups except between the 12- and 30-week-old groups. The same features were also seen in DM animals as the disease progressed. The total LI of controls were significantly higher and the number of suppressed stages was lower than those of DM animals, except among the 12-week-old group. Both aging and DM have depressing effects on the expression of PCNA in testicular tissue. The decline in PCNA expression is parallel with advancement of age and progress of DM. However, DM has a more suppressing effect than aging on that expression. This suppression could explain the decrease in male fertility potential that may be associated with both conditions.

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.

The immunohistochemical localization of transforming growth factor-beta 2 in the fetal and neonatal rat testis

The localization of transforming growth factor beta-2 (TGF beta 2) in the fetal and neonatal testis (from day 13.5 of fetal life to postnatal day 9) was investigated by an immunohistochemical staining method employing a specific polyclonal antibody. Immunostaining appeared on fetal day 13.5 in primitive Sertoli cells as they begin to come in contact with each other and surround the germ cells to form the seminiferous cords. Staining in Sertoli cells was still clearly observed until fetal day 16.5 and became faint or undetectable from fetal day 18.5 onwards. In fetal-type Leydig cells, a positive reaction for TGF beta 2 appeared on day 16.5 and became very intense from day 18.5 onwards. In the germ cells, immunoreactivity for TGF beta 2 appeared on fetal day 20.5, rose to a maximum on postnatal day 4 and decreased thereafter. On postnatal day 9, staining was still present in type A spermatogonia and absent in type B spermatogonia. No immunoreactivity was detected in peritubular cells on any day studied. In conclusion, our results are in favour of an autocrine/paracrine role of TGF beta 2 in the differentiation of the testis during the perinatal period. It may be involved in the organization of the seminiferous cords, the regulation of testosterone production and the regulation of the number of germ cells. When compared with the immunolocalization of TGF beta 1 that we have previously reported [1], the present study suggests that the roles of TGF beta 2 in the developing rat testis can be specific but also overlap from those of TGF beta 1.