Androgens and postmeiotic germ cells regulate claudin-11 expression in rat Sertoli cells.

In the present study we investigated whether fetal exposure to flutamide affected messenger and protein levels of claudin-11, a key Sertoli cell factor in the establishment of the hemotesticular barrier, at the time of two key events of postnatal testis development: 1) before puberty (postnatal d 14) during the establishment of the hemotesticular barrier, and 2) at the adult age (postnatal d 90) at the time of full spermatogenesis. The data obtained show that claudin-11 expression was inhibited in prepubertal rat testes exposed in utero to 2 and 10 mg/kg x d flutamide. However, in adult testes, the inhibition was observed only with 2, and not with 10, mg/kg x d of the antiandrogen.

The mitochondrial-dependent pathway is chronically affected in testicular germ cell death in adult rats exposed in utero to anti-androgens.

In utero exposure to exogenous anti-androgenic compounds induces a wide range of abnormalities of the reproductive system, including hypospermatogenesis, cryptorchidism and hypospadias. By using rats exposed in utero to the anti-androgenic compound flutamide (0.4, 2 or 10 mg/kg per day), it has been shown that hypospermatogenesis in adult testes could be related to (i) a long-term apoptosis in germ cells but not in somatic Leydig and Sertoli cells as evidenced by the TUNEL approach and (ii) alterations in the mRNA and protein expression of pro- (Bax, Bak, Bid) and anti-apoptotic (Bcl-2, Bcl-w) members of the Bcl-2 family.

Alteration of lactate production and transport in the adult rat testis exposed in utero to flutamide.

Although it is established that in utero exposure to the antiandrogen flutamide induces alteration of spermatogenesis in the adult rat testis offspring, the cellular and molecular mechanisms involved in such an effect remain to be investigated. In the present paper, by using as model adult rats exposed in utero to flutamide (0, 2, 10 mg/kg per day), we have investigated the hypothesis that germ cell alterations could be related to defects of energy metabolism and particularly to defects of the production and transport of lactate. Lactate is a preferential energy substrate produced by Sertoli cells and transported to germ cells by monocarboxylate transporters (MCT).

Long-term apoptotic cell death process with increased expression and activation of caspase-3 and -6 in adult rat germ cells exposed in utero to flutamide.

Although it is established that in utero exposure to antiandrogenic compounds such as flutamide induces hypospermatogenesis in adult male rat offspring, the cellular and molecular mechanisms remain to be investigated. By using adult rats exposed in utero to flutamide (0.4, 2, 10 mg/kg.

Tumorigenic potential of carbaryl in the heterozygous p53 knockout mouse model.

The heterozygous p53 knockout mouse model was used to assess whether vascular tumors noted in a 2-year carcinogenicity study in CD-1 mice with carbaryl were induced through a genotoxic mechanism. This knockout mouse model was selected for carbaryl because of the high sensitivity of this model to genotoxic events and its low spontaneous incidence of tumors until 9-12 months of age. Carbaryl was administered continuously via the diet to groups of 20 male heterozygous p53 knockout mice at concentrations of 0, 10, 30, 100, 300, 1000 and 4000 ppm for 180 days.

The development of methods for assessing the in vivo oestrogen-like effects of xenobiotics in CD-1 mice.

The increasing awareness and concern about the potential health risks posed to the ecosystem and to man by endocrine disrupting chemicals with oestrogen-like activity in the environment has focused attention on the need for developing sensitive and specific methods for identifying these xenobiotics and to evaluate their degrees of toxic effects. We have conducted dose response studies in immature (21 days old) CD-1 female mice treated with four compounds, diethylstilboestrol (DES) (0.1 microg to 25 mg/kg body weight), alpha-zearalanol (0.

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.

Time-course effects of human recombinant luteinizing hormone on porcine Leydig cell specific differentiated functions.

Since recombinant hormones are considered as safer and more reliable in their bioactivity than extractive hormones, the recently available human recombinant luteinizing hormone (r-hLH), will probably replace hCG in the near future, for clinical purposes. This prompted us to investigate whether or not, and by which mechanisms, r-hLH can induce a desensitization of signal transduction and/or an up-regulation of steroidogenic capacity in Leydig cells. The effects of a 30 min to 24 h exposure to r-hLH (10(-9) M) on the differentiated functions of cultured immature porcine Leydig cells were studied by measuring the following parameters: LH/hCG receptor number and mRNA, hCG-, cholera toxin- and forskolin-induced cAMP production, G protein alphas subunit content of the membrane, hCG-, cholera toxin-, forskolin-, 8Br-cAMP-, 22R-OH-cholesterol-, progesterone-, 170H-progesterone-, DHEA-, delta4-androstenedione-induced testosterone secretion and StAR, 3beta-HSD, cytochrome P-450scc and P-450c17 mRNAs.

Stimulating effect of both human recombinant inhibin A and activin A on immature porcine Leydig cell functions in vitro.

In addition to the regulation of FSH secretion, it has been clearly shown that inhibin and activin have paracrine/autocrine effects in the gonads. We have studied the effect of human recombinant inhibin A and human recombinant activin A on immature porcine Leydig cells in vitro. Leydig cells were prepared by collagenase digestion of testes from 3-week-old piglets, purified on Percoll gradient, then cultured in a chemically defined medium.

Regulation of intestinal cholecystokinin gene expression by glucocorticoids.

The effect of glucocorticoids on the expression of intestinal cholecystokinin (CCK) was investigated both in vivo and in cell culture systems. In vivo, 2-day administration of methylprednisolone to adult male rats induced a decrease in CCK-like immunoreactivity (CCK-L1) and CCK mRNA levels in mucosal extracts. In two CCK-producing cell lines, RIN 1056E and STC-1 of pancreatic and intestinal origin respectively, dexamethasone induced dose-dependent decreases in both CCK-L1 and steady-state CCK mRNA levels.

Regulation by gonadotropins of the messenger ribonucleic acid for P450 side-chain cleavage, P450(17) alpha-hydroxylase/C17,20-lyase, and 3 beta-hydroxysteroid dehydrogenase in cultured pig Leydig cells.

The Leydig cell from the immature pig provides a good model for studying testicular steroidogenesis. Regulation of the enzymes involved, which has been well studied in rodents, has not been characterized in the pig. The objectives of this study were to examine the regulation of three steroidogenic enzymes in pig Leydig cells by LH/hCG and testosterone.

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

Recent data have shown that Leydig-cell-specific functions, and therefore steroidogenic capacity, can be regulated by lutropin/human choriogonadotropin collectively termed gonadotropin and by several growth factors that are produced by and act within the testis. However, the molecular mechanisms by which these factors regulate Leydig cells are not understood. In the present study, we have investigated the effects of basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), insulin-like growth factor I (IGF-I) and transforming growth factor beta (TGF-beta) on mRNA for the gonadotropin receptor and three steroidogenic enzymes: cytochrome P-450scc, cytochrome P-450 17 alpha-hydroxylase/C17-20 lyase (17 alpha-hydroxylase), and 3 beta-hydroxysteroid dehydrogenase.

[Paracrine regulation of Leydig cells].

In addition to the endocrine control of Leydig cell functions by LH, paracrine control of Leydig cell functions has been suspected from the indirect stimulatory effect of FSH on Leydig cells. Coculture experiments of Leydig and Sertoli cells and the effect of Sertoli cell conditioned media on Leydig cells confirmed the production by Sertoli cells of acute steroideogenic factor(s) and factors involved in the positive or negative control of Leydig cell differenciated functions. Characterization and purification of these paracrine factors has been until recently unsuccessful.

Transcription and post-transcriptional regulation of luteotropin/chorionic gonadotropin receptor by the agonist in Leydig cells.

Porcine Leydig, cultured in a chemically defined medium, express luteotropin/human chorionic gonadotropin (LH/hCG) receptor and mRNA transcripts of several sizes (7.6, 6.7, 5.