Effect Of Human Chorionic Gonadotropin Research Articles

Hormonal Regulation and Cellular Distribution of Connexin 32.2 and Connexin 32.7 RNAs in the Ovary of Atlantic Croaker

The in vitro effects of human chorionic gonadotropin (hCG) on ovarian connexin (Cx) 32.2 and 32.7 RNA levels and ovarian follicle maturation were assessed, and the cellular distribution of Cx transcripts in the ovary was determined. hCG caused a concentration-dependent induction of Cx32.2 RNA, which peaked coincidentally with the appearance of morphological indices of oocyte maturational competence (OMC). Cx32.2 RNA levels declined thereafter in all treatment groups, although this decline was not accompanied by the onset of germinal vesicle breakdown (GVBD) at the lowest hCG concentration used. The levels of Cx32.7 RNA initially declined and subsequently increased to preincubation values after hCG treatment, but these changes were not dependent on hCG concentration. In a separate experiment, the decline in Cx32.7 RNA occurred in the presence or absence of hCG and was prevented by low (physiological) concentrations of estradiol-17β (E2) or by protein kinase C (PKC) inhibitor, but was enhanced in the presence of high E2 concentrations or of PKC activator. These changes in Cx32.7 RNA abundance were not associated with any indices of oocyte maturation. In situ hybridization of tissue sections showed the presence of Cx32.2 and Cx32.7 RNA in somatic cells of the ovarian follicle but not in oocytes. Cx32.2 RNA seemed to be present in granulosa and thecal cells, but the assay resolution was insufficient to reliably determine the distribution of Cx32.7 transcript by somatic cell type. In view of earlier findings that Cx32.2-based (but not Cx32.7-based) connexons can form functional homotypic channels, these results indicate that Cx32.2 gene expression in granulosa cells is sufficient for the formation of homologous gap junctions (GJ). Northern blot of RNA extracts from ovulated eggs, which are free of follicle cells, showed the presence of relatively low levels of both Cx RNAs. Thus, it is possible that Cx32.2 is present in oocytes and that it participates in heterologous (homotypic) GJ formation between the oocyte and the granulosa cells. In conclusion, Cx32.2 RNA levels in somatic cells of the ovarian follicle correlated positively with morphological indices of OMC acquisition, but subsequently declined during GVBD. These changes in Cx32.2 RNA may function in the regulation of GJ contacts during follicular maturation.

The Effects of Human Chorionic Gonadotropin on Thyroid Function Tests—an In Vivo Study

Objectives: There is considerable controversy of thyrotropin (TSH)-like action of human chorionic gonadotropin (hCG). There were found homology between hCG and TSH, and their receptors. Although there are many clinical and research data that support TSH-like activity of hCG, some researches have not supported this hypothesis. The objective of this study was to investigate of relationship between exogenous hCG and thyroid function tests in vivo conditions.

Human chorionic gonadotropin induces nitric oxide synthesis by murine microglia

This study investigated the effects of human chorionic gonadotropin (hCG) on the synthesis of nitric oxide (NO) in murine neonatal microglial cells. When hCG was used in combination with interferon-γ (IFN-γ), there was a marked cooperative induction of NO synthesis in a dose-dependent manner. This increase in NO synthesis was reflected as an increased amount of iNOS protein. The increase of NO synthesis by IFN-γ-plus-hCG was associated with the increase of tumor necrosis factor-α (TNF-α) secretion and hCG-induced NO production was decreased by the treatment with anti-murine TNF-α neutralizing antibody. This study provides evidence that hCG activates expression of iNOS protein in murine microglial cells accompanied by NO accumulation via pathway dependent on l-arginine in the culture medium, and further offers that TNF-α acts on the NO synthesis from IFN-γ-primed murine microglial cells.

Induction of superoxide dismutase by decidualization in human endometrial stromal cells.

The present study was undertaken to investigate the effect of decidualization on superoxide dismutase (SOD) expression in human endometrial stromal cells (ESC). To induce decidualization, isolated ESC were incubated with medroxyprogesterone acetate (MPA, 10(-6) mol/l) and oestradiol (10(-8) mol/l) for 23 days. Insulin-like growth factor-binding protein-1 (IGFBP-1) was used as a marker of decidualization. SOD mRNA in ESC was significantly increased on day 12 of the hormone treatment (P < 0.01), which was concomitant with the onset of IGFBP-1 mRNA expression, and further increased until day 23 of the treatment in a manner similar to the change in IGFBP-1 expression. To examine the synergistic effect of human chorionic gonadotrophin (HCG) with MPA and oestradiol on SOD and IGFBP-1 expression, ESC were incubated with HCG in the presence or absence of MPA and oestradiol. HCG had no synergistic effect on SOD and IGFBP-1 expression. SOD activities in the decidualized endometrial tissue obtained from patients given oestradiol and progesterone for 7-10 days were significantly higher than those in the non-decidualized endometrial tissue from patients without the hormone treatment (P < 0.01). In conclusion, SOD expression in ESC was induced by MPA and oestradiol accompanied by decidualization, suggesting that SOD may play important roles in decidualization of ESC.

The effects of human chorionic gonadotropin and interleukin-1beta on production of macrophage migration inhibitory factor by human granulosaluteal cells

The effects of human chorionic gonadotropin and interleukin-1beta on production of macrophage migration inhibitory factor by human granulosaluteal cells

Superoxide dismutase expression in the human corpus luteum during the menstrual cycle and in early pregnancy

To investigate the possible role of the superoxide radical and its scavenging system in the human corpus luteum, superoxide dismutase (SOD) values and lipid peroxide concentrations were analysed in the corpora lutea during the menstrual cycle and in early pregnancy. Copper-zinc SOD (Cu,Zn-SOD) activities increased from the early to mid-luteal phase, and gradually decreased thereafter and were the lowest in the regression phase. In pregnant corpus luteum, Cu,Zn-SOD activities were significantly higher than those in the mid-luteal phase. In contrast, manganese SOD (Mn-SOD) activities were low in the mid-luteal phase and increased toward the regression phase. Changes in mRNA expression of both types of SOD were similar to changes in their activities. Lipid peroxide concentrations were the highest in the regression phase whereas they were remarkably low in pregnant corpus luteum. The effects of human chorionic gonadotrophin (HCG) on luteal SOD were studied in vitro. HCG significantly increased Cu,Zn-SOD expression in mid-luteal phase corpora lutea, but not in late luteal phase corpora lutea. In conclusion, the present study suggests that the superoxide radical and its scavenging system, especially Cu,Zn-SOD, play important roles in the regulation of human luteal function. The stimulation of luteal Cu, Zn-SOD expression by HCG may be important in maintaining luteal cell integrity when pregnancy occurs.

Inhibition Of Apoptosis In Cultured Immature Rat Leydig Cells By Human Chorionic Gonadotropin Associated With Bcl-2 Mrna Expression

Bcl-2 is the first identified negative regulator of apoptotic cell death. When the level of Bcl-2 mRNA in rat whole testes was examined in the present study, it gradually decreased in rats from 2.5 to 9 weeks old. We also examined the effect of human chorionic gonadotropin (hCG) on apoptosis and the level of Bcl-2 mRNA expression in immature Leydig cells in vitro. When the cells were cultured with serum free media (SFM), Bcl-2 mRNA levels gradually decreased. On the other hand, the level of Bcl-2 mRNA in cells treated with 50 ng/ml of hCG decreased at 6 h, but increased after 12 h. At 24 h, the level of Bcl-2 mRNA in the treated cells was almost the same as that of control cells (time = 0). At 12 h after the addition of various concentrations (from 0.1-1000 ng/ml) of hCG, Bcl-2 mRNA levels increased in a dose-dependent manner. An analysis of DNA fragmentation showed that treatment with hCG prevents the apoptosis of immature Leydig cells. Our findings suggest that Bcl-2 mRNA may be related to the programmed cell death of immature rat Leydig cells in vitro, which are inhibited by hCG.

Regulation of Gap Junctions and Oocyte Maturational Competence by Gonadotropin and Insulin-like Growth Factor-I in Ovarian Follicles of Red Seabream

The in vitro effects of human chorionic gonadotropin (hCG) and human insulin-like growth factor-I (IGF-I) on the formation of oocyte–granulosa cell (heterologous) and granulosa cell–granulosa cell (homologous) gap junctions (GJ) were determined during the course of development of oocyte maturational competence (OMC) in ovarian follicles of red seabream. Incompetent, full-grown follicles were incubated in hCG (10 IU/ml), IGF-I (10 nM), or hormone-free medium for 0, 6, and 12 h and examined by electron microscopy. Qualitative analysis indicated that homologous and heterologous GJ were relatively rare in incompetent follicles and remained rare if they were maintained in control medium. However, both types of GJ were readily observed in follicles treated with hCG or IGF-I. For quantitative analysis, we measured changes in the combined numbers of both GJ types, since discrimination between the two was not always possible. The numbers of GJ along 125 μm of granulosa cell–zona radiata border were counted in three follicles/treatment. GJ markedly increased with time in the presence of hCG or IGF-I but not in control medium (Duncan's multiple range test; P<0.05). Functional assays confirmed that the hormonal treatments also induced OMC. Naturally competent follicles sampled at the appropriate stage of the reproductive cycle contained high levels of both types of GJ suggesting that the OMC-associated increase in GJ is physiologically relevant. In view of similar, earlier results with the Atlantic croaker, the present results support the concept that an increase in homologous and heterologous GJ is a general developmental event associated with the acquisition of OMC in teleost ovarian follicles. Also, a novel finding of this study is that IGF-I can regulate heterologous and homologous GJ in intact ovarian follicles.

Ceasing of movement-disorder attacks immediately after the onset of pregnancy: possible effect of human chorionic gonadotropin

In a woman with paroxysmal kinesiogenic choreoathetosis, attacks ceased within a few days after conception. An effect of human chorionic gonadotrophin is assumed, since this hormone decreased sodium currents and excessive action potential generation in an experimental approach.

Effects of human chorionic gonadotropin (hCG) and phenobarbital on the reproductive performance of fat-tailed Ghezel ewes

Increased ewe prolificacy and lambing rates, under certain conditions of sheep husbandry, may be economical and desirable. This paper reports on the effects of human chorionic gonadotropin (hCG) and phenobarbital (PB) on fertility and lambing rate in fat-tailed Ghezel sheep. One-hundred and five cyclic ewes (1.5 to 7.5 years of age) were randomly allotted to seven groups. Estrus was synchronized with two intramuscular injections of a prostaglandin F 2α analogue (PGF 2α), eight days apart. Four groups were randomly assigned to the hCG and three groups to PB experiments. Twenty-four hours after the second injection of PGF 2α, the ewes in four groups were injected (i.m.), either with 1 ml normal saline (control) or with 125, 250 or 500 IU hCG. Prolificacy of the ewes which conceived at first estrus increased in ewes receiving 500 IU of hCG, as compared with control group (an increase of 0.5 lamb/ewe) but fertility and lambing rate decreased in hCG-treated groups ( P<0.05). Nine days after the second injection of PGF 2α, ewes in the three remaining groups were orally fed empty gelatin capsules (control), 1.0 or 1.5 g of PB per day until the next estrus. Prolificacy and lambing rate increased ( P<0.05) in ewes which received 1.0 g of PB (1.57 and 146.5%, respectively), as compared with the control groups (1.17 and 100.3%, respectively). It is concluded that daily feeding of 1.0 g of PB from day 7 of the estrous cycle until the next estrus period is an effective method of increasing lambing rate. hCG also increases the prolificacy, but it greatly decreases fertility and lambing rates. Since hCG is more convenient to administer on a flock basis, further experiments to improve its efficacy are warranted.

Effect of human chorionic gonadotropin on cytokine production from human endometrial cells in vitro.

To examine whether human chorionic gonadotropin (hCG) is involved in the regulation of interleukin (IL)-6, tumor necrosis factor (TNF)-alpha, and leukemia inhibitory factor (LIF) secretion from cultured human endometrial cells. A mixed population of endometrial cells from six in vitro fertilization/embryo transfer patients was cultured and incubated with various doses of hCG (0, 1, 10, 50, 100, and 500 IU/ml) for 24 hr. IL-6, TNF-alpha, and LIF levels in the culture medium were measured with enzyme-linked immunosorbent assay. IL-6 and TNF-alpha levels were stimulated by hCG in a dose-dependent manner. Stimulation of IL-6 and TNF-alpha levels by 500 IU/ml of hCG increased their production by 3.7- and 2.8-fold, respectively (P < 0.05). Stimulation of IL-6 by 100 IU/ml of hCG was also significant (P < 0.05). However, there was no significant effect of hCG on LIF secretion by endometrial cells (P = 0.31). hCG is involved in the regulation of endometrial cytokine production from human endometrial cells in vitro. This finding supports the recently emerging notion that hCG could have important local roles within the uterus besides its well-known luteotrophic role on the corpus luteum for maintenance of pregnancy.

Hormonal regulation of connexin-43 in baboon corpora lutea.

The synthesis and secretion of progesterone in the corpus luteum are regulated by both endocrine and paracrine/ autocrine factors which affect the steroidogenic cells. Evidence suggests that these cells communicate via cell-cell junctional proteins, the connexins. Previously we have shown that connexin-43 is expressed in both human and baboon (Papio hamadryus anubis) corpora lutea, with differential expression throughout luteal development, but is not detectable in corpora albicantia. We have examined the effect of human chorionic gonadotropin (hCG), oxytocin, clomiphene citrate and the anti-progesterone onapristone on expression of connexin-43 protein in the early luteal phase 1-5 days after the mid-cycle luteinizing hormone (LH) surge (LH+ 1-5 days), the mid-luteal phase 6-10 days after the LH surge (LH+ 6-10 days), and the late luteal phase 11-15 days after the LH surge (LH+ 11-15 days) in corpora lutea obtained from normal adult cycling females. Connexin-43 was localized by immunohistochemistry in cultured cells from all the three stages. Western blot analysis of the treated cells indicated the presence of two bands at 43 and 45 kDa. The band at 45 kDa was found to be phosphorylated connexin-43, indicating the presence of functional gap junctions. hCG (10 IU/ml) stimulated the expression of connexin-43 throughout luteal development; however, maximum expression occurred in the early luteal phase with a significantly greater expression of the non-phosphorylated protein. In contrast, in the mid-luteal phase, the expression of the phosphorylated protein was predominant. Oxytocin (200 mU/ml) also stimulated connexin-43 expression throughout luteal development with similar effects on the phosphorylated and non-phosphorylated protein in the early and mid-luteal phase; however, compared with hCG, oxytocin had a greater effect on mid-luteal phase connexin-43 expression. In the presence of both hCG and oxytocin, the expression of connexin-43 was significantly higher than the control only in the late luteal phase. Both clomiphene citrate and onapristone suppressed connexin-43 expression, and concomitant addition of hCG did not counteract their effect. In the context of our previous studies, it is concluded that, together with LH/hCG and the steroid hormones, oxytocin is involved in cell-cell contact-dependent communication in the corpus luteum.

Inductions of immediate early genes (IEGS) and ref-1 by human chorionic gonadotropin in murine Leydig cell line (MA-10).

The effect of human chorionic gonadotropin (hCG) on the expression of immediate early genes (IEGs) including all members of fos and jun family, and c-myc was studied using mouse Leydig cell line (MA-10 cells) by Northern blot analyses. In addition, the induction of ref-1 which enhances DNA binding of fos/jun proteins was also analyzed. HCG induced a rapid and transient expression of c-fos, fosB, c-jun, junB, junD and c-myc with a peak at 30 min to 1 h. In contrast, induction of fra-1 mRNA was delayed with a peak at 3 hr. However, fra-2 mRNA was immediately increased by hCG with a peak at 1 h. The ref-1 mRNA was expressed before the stimulation and its level was not altered by hCG at least for 8 hr. The differential induction of IEGs and continuous expression of ref-1 mRNA suggest an important role of their gene products on the regulation of Leydig cell function by hCG.

The dynamics of in vitro 17 β-estradiol secretion by isolated ovarian follicles of the rainbow trout (Oncorhynchus mykiss)

This study investigated the effects of human chorionic gonadotropin (hCG), 17-hydroxyprogesterone (17P) and testosterone (T) on the in vitro production of 17β-estradiol (E2) by isolated ovarian follicles of the rainbow trout (Oncorhynchus mykiss). 17P at 100 ng ml-1, and hCG at 100 IU ml-1 stimulated E2 production relative to controls, whereas lower doses were ineffective. T was the most effective in stimulating E2 production, followed by 17P and hCG respectively. The timecourse of E2 production was investigated for both static culture, and incubations with media replacement, with follicles being exposed to hormone treatment for 30 min, 1 or 3 h, or constantly. E2 production was observed after 30 min, 3 and 3-6 h in response to T, 17P and hCG respectively. Under static culture, E2 levels reached maximal levels in 6 h. Longer incubations resulted in further metabolism of E2 to E2-glucuronide, which resulted in the blurring of treatment effects after 18 h. Incubations with media replacement resulted in higher E2 production than in static culture. The results indicate that a 6 h incubation period is sufficient to produce significant increases in E2 production in response to hCG, 17P and T, and that incubations longer than 12 h result in losses E2 from the incubation media. These findings have implications for the validity of using static cultures to examine the effects of hormone treatment on the activity of steroid converting enzymes in vitro.

Integrin alpha5 is expressed on human luteinizing granulosa cells during corpus luteum formation, and its expression is enhanced by human chorionic gonadotrophin in vitro.

We previously reported that human granulosa cells (GC) express integrin alpha6beta1, in large follicles and early corpus luteum (CL). In this study, we examined the expression of integrin alpha5 and fibronectin (FN) by immunohistochemistry. Integrin alpha5 was undetectable on human GC in preovulatory follicles, but it was intensely expressed on luteinizing GC of CL in the early luteal phase, and it was weakly expressed on large luteal cells (LL) in the midluteal phase. FN was similarly expressed between GC/LL. Thus, integrin alpha5 and FN were stage-specifically expressed on/between luteinizing GC in the early luteal phase. Next we examined the effect of human chorionic gonadotrophin (HCG) on expression of integrin alpha5 on luteinizing GC in vitro. GC obtained from preovulatory follicles were cultured for 3 days without (control) or with HCG (1 IU/ml), and expression of integrin alpha5 was examined by flow cytometry. Although the positivity rate did not differ, the mean relative fluorescence intensity was 3.4-fold higher in the HCG-treated group (n = 8, P < 0.01). These findings indicate that integrin alpha5 is rapidly expressed on GC during luteinization, probably under LH stimulation, and suggest that integrin alpha5 is involved in CL formation via interaction with its ligand FN.

THE EFFECT OF HUMAN CHORIONIC GONADOTROPIN ON METHOTREXATE CONCENTRATION IN THE RAT TESTES

We analyzed the effect of human chorionic gonadotropin (hCG) on drug concentrations in testicular interstitial fluid and whole testis tissue samples in rats receiving hCG prior to methotrexate (MTX) administration and in animals that did not receive hCG. Adult male Sprague-Dawley rats were injected subcutaneously with 200 i.u. hCG (Goldline Laboratories, Ft. Lauderdale, FL.). Controls were injected subcutaneously with normal saline (0.2 cc). Sixteen hours after injection, each rat was given methotrexate (Methotrexate LPF, Immunex Corp. Seattle WA.) via a carotid artery cannula in a dose of 30 mg./kg. Methotrexate (MTX) levels were collected 60 minutes post infusion time in 27 rats and 90 minutes post infusion in 27 rats. MTX levels were measured in serum, testicular interstitial fluid and testicular tissue. MTX levels were measured using high performance liquid chromatography (HPLC). A significantly higher concentration of MTX was found in testicular interstitial fluid (TIF) in rats injected with hCG when specimens were collected 60 minutes post infusion. MTX levels in TIF had reversed 90 minutes post infusion with higher levels found in control rats. Tissue levels of MTX demonstrated no significant difference at either 60 or 90 minutes in the hCG treated animals or controls. Our results suggest that hCG effects the tissue distribution of MTX within the testis. Human chorionic gonadotropin may have this effect on the testicular microvasculature by 1) selectively increasing capillary permeability, 2) increasing lymphatic flow within the testes or 3) increasing testicular blood flow.

Effects of hCG and β-hCG on IL-2 and sIL-2R secretion from human peripheral blood mononuclear cells: A dose-response study in vitro

The effects of human chorionic gonadotropin (hCG) as well as β-subunit of hCG (B-hCG) in concentrations of: 80000 25000 ; 500; 50; 5 mIU/ml on in vitro release of interleukin-2 (IL-2) and soluble interleukin-2 receptor (sIL-2R) from resting or phytohemagglutinin (PHA) activated human peripheral blood mononuclear cells (PBMC) were studied. Both the interleukins were measured in supernatants of human PBMC by quantitative sandwich enzyme immunoassay method (ELISA). We found that hCG in the dilutions of 80000 mIU/ml ( P < 0.01) and 5 mIU/ml ( P < 0.05) diminished IL-2 secretion only from PHA activated PBMC. β-hCG in concentrations of 5 mIU/ml ( P < 0.05), 500 mIU/ml ( P < 0.01) and 25000 mIU/ml ( P < 0.05) also diminished IL-2 secretion from PHA activated PBMC, and only in a dilution of 25000 mIU/ml ( P < 0.05) from resting PBMC. Simultaneously, hCG in concentration of 80000 mIU/ml ( P < 0.01) potentiated the release of sIL-2R into supernatants from resting and PHA activated PBMC, but in concentration of 50 mIU/ml ( P < 0.05) slightly depressed the secretion of IL-2 from PHA activated PBMC cultures. β-hCG in dilution of 25000 mIU/ml ( P < 0.001) stimulated the release of sIL-2R from resting or PHA activated PBMC. β-hCG had also inhibitory effect on sIL-2R secretion from resting (in a dilution of 50 mIU/ml; P < 0.05) and PHA activated (500 mIU/ml; P < 0.01) PBMC. The inhibitory effect of very high concentrations of hCG and β-hCG on IL-2 secretion together with their stimulatory effect on sIL-2R release from PBMC may be an important event during the human pregnancy and various cancers.

Paracrine effect of human chorionic gonadotropin ectopically produced from papillary thyroid cancer cells on growth and function of FRTL-5 rat thyroid cells.

It is well known that human chorionic gonadotropin (hCG) is sometimes secreted from nontrophoblastic neoplasms. To elucidate the role of ectopic hCG, we investigated the effect of hCG produced from a papillary thyroid cancer cell line (B-CPAP cells) on stimulation and growth promotion of FRTL-5 rat thyroid cells. Ectopic hCG contained in the culture medium of B-CPAP cells was purified using gel filtration and bioassayed for thyrotropic activity in FRTL-5 cells. Addition of ectopic hCG (up to 5.2 x 10(4) IU/L) increased cyclic adenosine monophosphate (cAMP) accumulation and 3H-thymidine incorporation in FRTL-5 cells dose dependently. These effects were almost as potent as the stimulation induced by standard hCG CR-127. After the absorption of the ectopic hCG by anti-hCG-beta monoclonal antibody, the cAMP accumulation was significantly decreased. Analysis of ectopic hCG isoforms with different isoelectric points indicated the predominance of the acidic hCG isoform with isoelectric point (pI) 3.8-3.2 that is the major isoform of standard hCG. Basic isoforms (pI 5.7-5.3) with higher thyrotropic potency were also detected. These results indicate that the ectopic hCG secreted from papillary thyroid cancer cells possess intrinsic thyroid-stimulating and growth-promoting activity. The ectopic hCG may act as an autocrine-paracrine factor in nontrophoblastic neoplasms.

Androgen action on the restoration of spermatogenesis in adult rats: effects of human chorionic gonadotrophin, testosterone and flutamide administration on germ cell number.

Spermatogonial proliferation is a critical but poorly understood determinant of the spermatogenic process. In rats, exogenous testosterone plus oestradiol (TE) markedly suppresses serum LH and testicular testosterone levels. In the TE-treated rat, spermatogonial number declines to approximately 65% of control levels while round to elongated spermatid maturation is interrupted. The partial restoration of testicular testosterone levels by exogenous testosterone administration restores spermatid maturation but neither testicular weight nor spermatogonial number are normalized. This study aimed to determine the role of testosterone and/or non-androgenic Leydig cell factors in the restoration of spermatogonial number in the testosterone-treated rat. Germ cell numbers were assessed using stereological methods and expressed as germ cell number per testis. Adult Sprague Dawley rats initially received 3 cm testosterone plus 0.4 cm oestradiol Silastic implants for 9 weeks to suppress spermatogenesis, followed by 10 days of either (i) exogenous testosterone using implants (T24 cm) or testosterone esters (5 or 25 mg sc every third day), or (ii) human chorionic gonadotrophin (hCG; 0.5, 1.25, 2.5 or 10 IU/kg sc daily) as an LH substitute to restore Leydig cell function. Following TE treatment, testicular weights and testicular testosterone levels were reduced to 31% and 1.3% of control levels, respectively. In response to exogenous testosterone administration, testicular weight was restored to 52-58% of controls while testicular testosterone levels increased to only 3.5-17.3% of controls despite serum testosterone levels 4.5-24-fold above control. In response to hCG treatment, a graded increase in testicular testosterone levels was achieved (2.6-20.5% of control) and testicular weights increased to 38-56% of control. TE suppression reduced (p < 0.05) type A spermatogonia and type B spermatogonia/preleptotene spermatocyte numbers per testis to 61% and 77% of control, respectively; however, neither subsequent testosterone nor hCG treatments significantly increased either germ cell number. In a second study, hCG (1.25 IU/kg) was administered alone or in combination with the androgen receptor antagonist, flutamide (100 mg/kg sc daily), to withdraw androgenic effects at all stages of spermatogenesis. The TE-induced suppression of type A spermatogonia (59% control) and type B spermatogonia/preleptotene spermatocytes (68% control) was not affected by hCG +/- flutamide. On the other hand, as expected, hCG increased the number of elongated spermatids (p < 0.05). The co-administration of flutamide reduced (p < 0.05) the numbers of all pachytene spermatocyte forms, round and elongated spermatids below those of TE-treated animals. We conclude that neither exogenous testosterone nor hCG is capable of restoring spermatogonial number in the TE-treated rat within 10 days despite the partial or full restoration of testicular testosterone levels. No evidence was found for the involvement of non-androgenic Leydig factors in the control of spermatogonial numbers. The data from flutamide-treated animals demonstrates that residual androgen effects are present in the TE model as, even in the presence of testicular testosterone levels below that needed for spermatid maturation, further inhibition of spermatocyte development and meiosis is apparent.

Biological effects of human chorionic gonadotropin and its synthetic peptide fragment on HL-60 cells

Human chorionic gonadotropin and synthetic fragment of its β-subunit consisting of 18 amino acids (from the 128th to 145th residue) inhibit the growth of promyeloid HL-60 cell line and compete for the common binding sites on the plasma membrane of HL-60 cells.