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H Billig

Publications and source records attributed to H Billig.

At least 55 records · Page 3Linked to original sources
PubMed1991

Expression and regulation of growth hormone (GH) receptor messenger ribonucleic acid (mRNA) in rat adipose tissue, adipocytes, and adipocyte precursor cells: GH regulation of GH receptor mRNA.

The effects of hypophysectomy and hormonal replacement therapy on GH receptor (GH-R) gene expression was studied in rat adipose tissue with a cRNA probe corresponding to the amino-terminal of the hepatic GH-R. Male Sprague-Dawley rats, 50-65 days of age, were used. In all fat depots tested (epididymal, retroperitoneal, and sc), two transcripts with an estimated size of 4.0 and 1.2 kilobases (kb), respectively, were detected. An intermediate-size transcript (2.6 kb) was sometimes observed. Also, isolated adipocytes and adipocyte precursor cells from the epididymal fat pad expressed these GH-R transcripts. The pituitary dependance of GH-R gene expression was analyzed in epididymal fat. Hypophysectomies were performed at 50 days of age, and the rats were then given replacement therapy with L-T4 (10 micrograms/kg.day) and hydrocortisone (400 micrograms/kg.day). Hypophysectomy decreased the abundance of both the 4.0 and the 1.2-kb transcripts, an effect that in part was restored by GH treatment. A solution hybridization RNase protection assay was then used to further characterize the effect of GH treatment of hypophysectomized rats on GH-R gene expression. A single injection of human GH (100 micrograms/rat) increased GH-R mRNA levels within 1 h, and maximal levels were reached between 3-12 h after the injection. The increase in GH-R mRNA levels was dose dependent and was observed also after prolonged treatment (1 or 5 mg/kg.day for 6 days) with bovine GH. These results confirm that GH-R mRNAs are present in rat adipose tissue from different fat depots. GH-R transcripts of the same estimated size were detected in isolated adipocytes and adipocyte precursor cells. Furthermore, the results show that there is a rapid and GH-dependent regulation of GH-R mRNA levels in adipose tissue.

Adipose Tissue↗
PubMed1990

Expression of the growth hormone-binding protein messenger RNA in the liver and extrahepatic tissues in the rat: co-expression with the growth hormone receptor.

A cDNA encoding a growth hormone-binding protein (GH-BP) was recently cloned from mouse and rat liver. The GH-BP in these species is identical to the extracellular part of the GH receptor (GH-R) with the transmembrane and intracellular domain substituted for a hydrophilic tail. In the present study the expression of the GH-BP and GH-R was studied in rat liver and extrahepatic tissues. Specific transcripts with estimated sizes of 1.2 kb (GH-BP) and 4.0 kb (GH-R) were found in the liver from both sexes. The expression of GH-BP increased with age up to puberty suggesting that it is developmentally regulated in a similar manner as GH-R. GH-BP mRNA was found in all extrahepatic tissues examined that contained GH-R mRNA. The ratio between the 1.2 kb and 4.0 kb transcripts varied between tissues indicating that GH-R and GH-BP transcripts may be separately regulated. The co-expression of GH-BP and GH-R suggests a functional role for the GH-BP in the local regulation of GH action.

Age Factors↗
PubMed1990

Effects of follicle stimulating hormone and purines on rat oocyte maturation.

The presented data demonstrate a dose-dependent inhibition of spontaneous meiosis of cumulus-enclosed rat oocytes by guanosine, hypoxanthine, and adenosine. The inhibition by adenosine was transient whereas guanosine and hypoxanthine exerted a persistent effect over 24 h of incubation. The order of potency of the substances was guanosine greater than hypoxanthine greater than adenosine and the inhibition was reversible. The inhibitory effect was reduced when the cumulus cells around the oocyte were removed. The inhibition during the first 12 h of incubation was potentiated by FSH. However, at 24 h of incubation FSH partially overcame the inhibitory effect by hypoxanthine but did not influence the inhibitory effect by guanosine. Also 8BrcAMP potentiated the inhibitory effect observed by guanosine, hypoxanthine, and adenosine, suggesting that the potentiating effect of FSH was mediated via cAMP. Our data demonstrate that adenosine, hypoxanthine, and guanosine synergized with FSH in inhibiting spontaneous rat meiosis, as previously shown in mouse. FSH could partially overcome the inhibitory effect exerted by hypoxanthine but did not counteract the inhibitory effect of guanosine.

Adenosine↗
PubMed1990

Resumption of rat oocyte meiosis is paralleled by a decrease in guanosine 3',5'-cyclic monophosphate (cGMP) and is inhibited by microinjection of cGMP.

The aim of the present study was to measure the level of cyclic GMP (cGMP) compared with the level of cyclic AMP (cAMP) in rat oocytes during resumption of meiosis I (oocyte maturation) and to microinject these cyclic nucleotides into the oocyte to study their effects on oocyte maturation. Immature oocytes were obtained from prepubertal rats primed with pregnant mare's serum gonadotropin. OOcytes were isolated adn short-term cultured under conditions enabling spontaneous maturation. The levels of cGMP and cAMP decreased in the oocyte during spontaneous maturation (from 0.41 to 0.25 and from 0.64 to 0.42 fmol per oocyte respectively). The decrease was observed during the first hour of culture, and no further decline was seen after 2 h. Microinjection of cGMP or cAMP into isolated immature oocytes delayed the spontaneous maturation, cGMP being slightly more effective than cAMP, whereas 2-deoxy-cAMP (which does not stimulate protein kinase A) did not. These results demonstrate for the first time that the level of cGMP decreases in the oocyte parallel to spontaneous meiosis, as already shown for cAMP. This suggests that cGMP, as well as cAMP, may be of importance for regulating this process. This assumption is further supported by data demonstrating a delay in the maturation of oocytes injected with cGMP.

Animals↗
PubMed1990

Atrial natriuretic peptide inhibits spontaneous rat oocyte maturation.

We report results of experiments demonstrating a dose-dependent inhibition of spontaneous maturation (resumption of meiosis) in rat oocyte-cumulus complexes by atrial natriuretic peptide (ANP). The inhibition was persistent over the time period studied. The ANP analog Tyr8-ANP, which mediates smooth muscle relaxation in other organs without elevating cGMP levels, did not inhibit the spontaneous maturation. ANP, but not Tyr8-ANP, dose-dependently stimulated cGMP accumulation in oocyte-cumulus complexes. Furthermore, sodium nitroprusside (SNP), that stimulates a soluble form of guanylate cyclase, inhibited spontaneous maturation in oocyte-cumulus complexes and stimulated cGMP accumulation in oocyte-cumulus complexes. Neither ANP nor SNP stimulated cAMP accumulation. In oocytes where the surrounding cumulus cells had been removed neither ANP nor SNP inhibited the spontaneous maturation. These results demonstrate that cumulus cells, but not the oocyte itself, have ANP receptors and guanylate cyclases. Furthermore, ANP, via cGMP, can influence oocyte meiosis, suggesting a possible involvement of ANP and cGMP in the control of the meiotic process in rat oocytes.

Animals↗
PubMed1989

Adenosine as substrate and receptor agonist in the ovary.

In the present study the possible dual effects of adenosine as substrate and adenosine receptor agonist in rat granulosa cells, cumulus-oocyte complexes, luteal cells and ovarian membranes are discussed. Adenosine is an indispensable compound in cell energy metabolism, as precursor to cofactors, second messenger and nucleic acids. Adenosine is also an agonist to adenosine receptors. The adenosine receptor can either inhibit (A1) or stimulate (A2) adenylate cyclase. Alternatively, in some cells adenosine receptor activation is linked to other cellular events like inhibition of Ca2+ fluxes. Adenosine is taken up by isolated preovulatory granulosa and luteal cells from pregnant mare serum gonadotropin-treated immature rats, but follicle stimulating hormone (FSH) decreases the uptake by granulosa cells. Adenosine, but not the non-metabolizable adenosine analogs 5'-(N-ethyl)carboxamide-adenosine (NECA), 2-chloro-adenosine (2-Clado), N6-(R-phenyl-isopropyl)-adenosine (R-PLA) and N6-(S-phenyl-isopropyl)-adenosine (S-PLA), increase granulosa cell ATP levels. FSH and luteinizing hormone (LH) decrease granulosa cell ATP levels in the presence or absence of adenosine. It has previously been shown that FSH and LH decrease oxygen consumption by cumulus-oocyte complexes and increase their lactate production. These effects have been suggested to be due to a competition of cofactors (e.g. ADP) common to glycolysis and the respiratory chain. The fact that adenosine reverse the gonadotropin-induced effects on oxygen consumption and lactate production support this theory. Adenosine and its analogs increase cAMP accumulation in luteal and granulosa cells only in the presence of gonadotropins, and this effect is antagonized by the adenosine receptor antagonist 8-phenyl-theophylline (8-PHT). Furthermore, adenylate cyclase is stimulated by adenosine analogs in membranes from non-luteinized and luteinized ovarian membranes and in luteal cell homogenates. The effect of NECA is antagonized by 8-PHT. In the membranes, the rank order of potency was NECA greater than 2-Clado greater than R-PLA greater than S-PLA, suggesting adenosine A2 receptors. In summary, it is suggested that adenosine can act both as a substrate to intracellular metabolism and as an adenosine A2 receptor agonist in granulosa and luteal cells. A paracrine short loop positive feedback model is proposed where extracellular adenosine, derived from a gonadotropin-induced extracellular increase in cAMP and a decrease in cellular ATP, enhances gonadotropin stimulation in granulosa and luteal cells.

Adenosine↗
PubMed1989

Estrus cycle-dependent co-variation of insulin-like growth factor-I (IGF-I) messenger ribonucleic acid and protein in the rat ovary.

It has been suggested that insulin-like growth factor-I (IGF-I) exerts paracrine or autocrine actions in the ovary and may play a role in the regulation of ovarian function. We have examined ovarian levels of IGF-I mRNA and IGF-I protein throughout the estrus cycle. The lowest levels of IGF-I mRNA were found on proestrus (12.00 h). The mRNA levels on estrus (12.00 h) were significantly (P less than 0.05) higher than on proestrus. The correlation between the levels of IGF-I and IGF-I mRNA was linear and significant (r = 0.706; P less than 0.01). Our observations that the IGF-I gene expression and translation vary during the estrus cycle, with an increase between proestrus and estrus, suggest that the gonadotropin surge could be of importance for the regulation of IGF-I in vivo and that IGF-I may be involved in the cell proliferation and differentiation caused by these hormones.

Animals↗
PubMed1989

Adenosine receptor-mediated effects on adenylate cyclase activity in rat luteal tissue: a putative local regulatory role of adenosine in the corpus luteum.

The influence of adenosine analogs on adenylate cyclase activity was investigated in membrane preparations of luteinized ovaries and in cell homogenates of isolated luteal cells. The adenosine receptor agonist 5'-(N-ethyl)-carboxamido adenosine (NECA) dose-dependently stimulated adenylate cyclase activity in membrane preparations of 5-day-old luteinized ovaries with an apparent EC50 of 0.58 microM. The other adenosine analogs tested were less potent in stimulating the adenylate cyclase activity with the following rank order of potency: NECA less than 2-chloro-adenosine greater than N6-(R-phenyl-isopropyl)- adenosine less than N6 -(S-phenyl-isopropyl)-adenosine. In homogenates of isolated cells from 5-day-old corpora lutea, NECA stimulated adenylate cyclase with the same EC50 as in the membranes from luteinized ovaries. The effect of NECA was antagonized by the adenosine receptor antagonist 8-phenyltheophylline. In incubated luteal cells of both 2- and 5- to 6-day-old luteinized ovaries, NEC stimulated cyclic adenosine 3', 5'-monophosphate (cAMP) accumulation and markedly potentiated luteinizing hormone-stimulated cAMP accumulation. Progesterone synthesis was also stimulated by NECA in incubated cells. The study demonstrates effects of adenosine analogs on adenylate cyclase and cAMP accumulation that fulfill the criteria for adenosine A2 receptor-mediated effects in luteal cells and membranes. These data suggest that adenosine may have a local regulatory action in luteal tissue through adenosine receptor activation.

Adenosine↗
PubMed1989

Insulin-like growth factor I in the developing and mature rat testis: immunohistochemical aspects.

The distribution of insulin-like growth factor I (IGF-I; somatomedin C) was mapped in testes of different aged rats by using immunohistochemical techniques. The antiserum used, K 624, has been demonstrated to be specific for human IGF-I, as defined by several criteria. Antibodies to the M1 subunit of ribonucleotide reductase, a key enzyme in DNA synthesis, were used to visualize meiotic and mitotic cells. Cytoplasmic IGF-I-like immunoreactivity as demonstrable during the first two postnatal weeks in spermatogenic cells, in Sertoli cells, and in Leydig cells. The IGF-I-like immunoreactivity decreased in the Sertoli and Leydig cells during the third and fourth postnatal weeks, and in adult rats, only spermatogenic cells showed IGF-I-like immunoreactivity. In mature rat testes, the spermatocytes were strongly immunoreactive. During puberty and adulthood, the spermatogonia expressed subunit M1 ribonucleotide reductase immunoreactivity, whereas no IGF-I-like immunoreactivity could be detected. No extracellular immunoreactivity was observed. We propose that IGF-I and/or IGF-I-like substances, possibly formed by primary spermatocytes, are likely to be involved in differentiation processes, but not in the initiation of cell proliferation in adult testes. The autocrine and/or paracrine action of IGF-I and/or IGF-I-like substances may thus have different action in developing testes than in adult testes. Our results do, however, not allow firm statements about whether IGF-I and related substances exert their actions on Sertoli cells or spermatogenic cells.

Aging↗
PubMed1989

Plasma growth hormone pattern regulates epidermal growth factor (EGF) receptor messenger ribonucleic acid levels and EGF binding in the rat liver.

It has recently been shown that GH increases the number of available hepatic receptors for epidermal growth factor (EGF). In the present study the effects of the sexually dimorphic plasma GH pattern (higher pulsatility in male rats) on hepatic EGF binding and EGF receptor mRNA concentration were investigated. The specific binding of [125I]EGF to purified liver membranes was about 2-fold higher in male rats than in females on days 35, 50, and 80 of life. EGF receptor mRNA levels, as determined by an RNase protection solution hybridization assay, were higher in males only on days 47-50. Hypophysectomy on day 50 reduced the EGF receptor mRNA concentration to a level that did not differ between male and female rats. In hypophysectomized rats of both sexes, intermittent GH treatment (sc injections every 12 h for 7 days) enhanced hepatic EGF receptor mRNA concentrations to normal male levels, while continuous GH administration was less effective. Northern blot analysis indicated that transcripts with apparent sizes of 9.5 and 6.6 kilobases were dependent on the plasma GH pattern. Intermittent iv GH replacement therapy for 5 days given at 3-h intervals by an automatic iv infusion system increased the hepatic EGF receptor mRNA concentration as well as specific EGF binding, whereas continuous iv GH infusion was ineffective. These results show that a pulsatile plasma GH pattern, similar to that of male rodents, is markedly more effective in enhancing hepatic EGF receptor mRNA levels and EGF binding than a continuous feminine GH pattern. These results are consistent with a pretranslatory stimulation of EGF receptor synthesis by pulsatile GH.

Animals↗
PubMed1988

Immunohistochemical localization of insulin-like growth factor I in the adult rat.

Rabbit antisera against native human insulin-like growth factor I (IGF-I; somatomedin C) or a synthetic tetradecapeptide, representing the carboxyterminal amino acids 57-70 of human IGF-I, were used to map immunohistochemically the distribution of IGF-I immunoreactive material in adult rats. Both antisera were specific for IGF-I, as characterized by immunoabsorption, immunoblotting and radioimmunoassay. There was no cross-reactivity to IGF-II, relaxin or pro-insulin; substances having a high degree of structural homology with IGF-I. High IGF-I immunoreactivity was observed in spermatocytes of the testis; in oocytes, granulosa and theca interna cells of the ovary during early stages of follicle development; in some lymphocytes and in reticular cells of lymphoid and hematopoietic organs; in salivary gland duct cells; in the adrenal medulla, the parathyroid gland and the Langerhans' islets. Chondrocytes in the epiphyseal and rib growth plates and at articular surfaces showed strong IGF-I immunoreactivity. Brown but not white fat cells were stained. Nerve cells in the peripheral and autonomic nervous system showed faint to intense IGF-I immunoreactivity. In contrast, neurons and neuroglial cells in the central nervous system were generally negative; motor neurons being an exception. Erythropoietic, thrombocytopoietic and myeloic cells in the bone marrow showed IGF-I immunoreactivity, but only at defined developmental stages. Hepatocytes showed faint IGF-I immunoreactivity, but became more intensely stained after pretreatment with colchicine. The present results suggest that IGF-I is synthetized by cells in several tissues and organs in the adult rat. There was an apparent association between the localization of IGF-I and cell differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Evidence for A2 adenosine receptor-mediated effects on adenylate cyclase activity in rat ovarian membranes.

Effects of adenosine analogues on adenylate cyclase activity in preovulatory rat ovarian membranes were studied. Adenosine analogues stimulated adenylate cyclase activity in the following rank order of potency: NECA (5'-(N-ethyl)carboxamidoadenosine) greater than 2-chloroadenosine greater than N6-(R-phenylisopropyl)-adenosine greater than N6-(S-phenylisopropyl)adenosine. The apparent EC50 for NECA was 0.28 microM. The adenosine receptor antagonist 8-phenyltheophylline (10 microM) displaced the dose-response curve for NECA to the right, increasing the EC50 for NECA about one order of magnitude. NECA also additively increased maximally FSH-stimulated adenylate cyclase activity. These results suggest that adenosine stimulates adenylate cyclase in rat ovarian membranes via adenosine receptors of the A2 type.

Adenosine↗
PubMed1988

Adenosine receptor-mediated effects by nonmetabolizable adenosine analogs in preovulatory rat granulosa cells: a putative local regulatory role of adenosine in the ovary.

The influence of nonmetabolizable adenosine analogs on cAMP production was investigated in preovulatory rat granulosa cells. 5'-(N-ethyl)Carboxamido-adenosine (NECA), a stimulatory A2-adenosine receptor agonist, stimulated cAMP accumulation, and NECA and 2-chloro-adenosine also potentiated the response to FSH. The adenosine receptor antagonist 8-phenyltheophylline antagonized the effect of NECA, shown by a shift in the dose-response curve to the right. The stimulatory effect of NECA was also seen in an ovarian membrane preparation, where NECA stimulated adenylate cyclase in both the presence and absence of FSH. The stimulatory effect of NECA was also decreased by 8-phenyltheophylline in this preparation. The A1-receptor agonists N6-(R-phenyl-isopropyl)-adenosine (R-PIA) and N6-(S-phenyl-isopropyl)-adenosine (S-PIA) both inhibited FSH-stimulated cAMP accumulation. The inhibitory effects of R-PIA and S-PIA, but not the stimulatory effects of NECA, could be counteracted by dipyridamole, a nucleoside transport inhibitor. Furthermore, R-PIA and S-PIA inhibited adenosine uptake into granulosa cells. Thus, the inhibitory effects of R-PIA and S-PIA are not likely to be mediated via membrane-bound inhibitory A1-adenosine receptors. Neither the stimulatory effects of NECA nor the inhibitory effects of R- and S-PIA could be attributed to changes in ATP levels, since the ATP levels were unaffected by these analogs. The results of this study indicate the existence of stimulatory A2-adenosine receptors in preovulatory rat granulosa cells and suggest a membrane-associated modulatory role of adenosine in preovulatory granulosa cells.

2-Chloroadenosine↗
PubMed1986

Gonadotropin depression of adenosine triphosphate levels and interaction with adenosine in rat granulosa cells.

Cellular ATP levels were measured with the luceferin-luciferase enzyme method in incubated preovulatory granulosa cells in vitro from PMSG-treated immature rats. The ATP levels were depressed by both FSH and LH, FSH being the more effective. Adenosine enhanced the ATP levels about 3-fold, but the depressive effects of gonadotropins could not be overcome by the addition of adenosine. Uptake of adenosine in granulosa cells followed Michaelis-Menten kinetics, with a Km of 15.9 +/- 3.6 microM and a maximum velocity of 1.6 +/- 0.1 pmol/min X 10(5) cells. The half-time for uptake of adenosine was about 40 min. The maximal uptake of adenosine was lowered from 48 +/- 5 to 30 +/- 1 pmol/10(5) cells by FSH treatment of the cells. The basal secretions of cAMP and progesterone from the granulosa cells were slightly but significantly enhanced by adenosine alone. Adenosine markedly enhanced FSH-stimulated cAMP secretion, but not progesterone secretion. A nonmetabolizable adenosine analog, 2-chloro-adenosine, did not affect the ATP levels or the secretion of cAMP from granulosa cells. This study confirms previous observations that adenosine can increase ATP levels and amplify the response to gonadotropins in gonadal cells. A novel finding is that the levels of ATP in granulosa cells are markedly depressed by gonadotropins. It is speculated that this depression of ATP may be a factor in the metabolic control of granulosa cells.

Adenosine↗
PubMed1985

Gonadotropin-induced inhibition of oxygen consumption in rat oocyte-cumulus complexes: relief by adenosine.

In the cumulus-oocyte complex (COC), as well as in the whole ovarian follicle, gonadotropins stimulate glycolysis, measured as lactate accumulation. In contrast to this, COC oxygen consumption is decreased by gonadotropins. One possible explanation for this inhibition is a competition for a limited supply of cofactors, common for both the glycolytic pathway and the respiratory chain. In the present study, addition of adenosine to COCs cultured with gonadotropins restored the oxygen consumption to basal levels. This effect was specific for metabolizable adenosine. Other nucleosides or non-metabolizable 2-chloro-adenosine had no effect. Adenosine also increased ATP and decreased lactate accumulation by the COC. The nucleoside transport inhibitor dipyridamol abolished the effects of adenosine on oxygen consumption and ATP accumulation. Taken together, these results support the hypothesis that a relative lack of adenosine-derived cofactors is probably involved in the decrease of oxygen consumption in vitro by gonadotropin-stimulated cumulus cells.

Adenosine↗
PubMed1984

Effect of a GnRH analogue on rat granulosa cell lactate production in vitro.

The effect of a GnRH analogue [D-Ala6, des-Gly10-NH2)-GnRH-ethylamide,GnRHa) on granulosa and cumulus cell glycolysis in presence or absence of FSH was studied. Cumulus complexes and granulosa cells from PMSG-treated rats were cultured in Eagle's minimal essential medium (MEM) for a period of 72 h. Media were changed at 24 and 48 h and lactate content was assayed by fluorimetry. GnRHa alone stimulated lactate production in granulosa cells. GnRH combined with FSH increased lactate production in granulosa cells during the 0-24 h period and decreased it during the 48-72 h period as compared to FSH alone. GnRHa did not stimulate lactate production in cumulus complexes during 72 h culture in MEM, while FSH did. In a less complex culture medium, BMOC, GnRHa caused a small increase in lactate production and slightly enhanced the FSH effect. In conclusion, GnRHa has a direct stimulatory effect on granulosa cell glycolysis. GnRHa also modulates the FSH stimulation of granulosa cells biphasically, i.e. early enhancement (0-24 h) and late inhibition (48-72 h). GnRHa has no consistent direct effects on cumulus cell glycolysis.

Animals↗