Unimpaired postreceptor regulation of luteinizing hormone secretion by gonadotropin-releasing hormone and estrogen in aged rat anterior pituitary cells

Delayed, attenuated, or absence of the proestrous LH surge occurs in aging rats. To assess how aging affects the positive feedback action of 17 beta-estradiol (E2) on the pituitary, we determined the responsiveness of rat pituitary cells to GnRH and the secretagogues affecting intracellular signal transduction mechanisms in the presence or absence of E2. We also correlated the LH response to pituitary LH content. Anterior pituitaries excised from ovariectomized Sprague-Dawley rats, either young (3-4 months) or old (19-20 months), were enzymatically dispersed and then pretreated with or without E2 (0.6 nM) for 48 h, followed by incubation for 3 h with or without various secretagogues. The secretagogues included GnRH (1 and 10 nM), veratridine (increases Ca2+ influx; 5 and 10 microM), and phorbol 12-myristate 13-acetate (a protein kinase-C activator; 10 and 100 nM). LH in media and cells were measured by RIA and expressed on the basis of cellular DNA. GnRH, veratridine, and phorbol 12-myristate 13-acetate at all doses stimulated (P < 0.01) LH release in cells from both young and old rats. E2 stimulated (P < 0.05 to P < 0.01) all secretagogue-induced LH release in cells from both young and old rats, but only basal LH release (P < 0.05) in cells from young rats. The magnitude of both basal and secretagogue-induced LH release in either the presence or absence of E2 was smaller (P < 0.01) in cells from old than in those from young rats. The initial cellular LH was lower (P < 0.01) in cells from old than in those from young rats. The LH-releasing ability (expressed as a percentage of total cellular LH) of cells from old rats was identical (P > 0.05) to that of cells from young rats under all conditions studied. These results suggest that the reduced magnitude of LH release by cells from old rats may be attributed to reduced cellular LH, rather than to impaired estrogen feedback or impaired signal transduction mechanisms. It remains to be determined whether LH biosynthesis per cell and/or the number of gonadotropes decrease with age.     

Cytokine-mediated growth hormone release from cultured ovine pituitary cells

Previous studies have demonstrated that intravenous lipopolysaccharide (LPS) will increase concentrations of growth hormone (GH). One possible explanation for this may reside in the response of the pituitary to specific cytokines. This study sought to determine the effects of recombinant bovine tumor necrosis factor alpha (TNF), recombinant ovine (ro) interleukin-1alpha (IL-1alpha), roIL-1beta, ro interleukin-2 (IL-2), and ro gamma-interferon (INT) on GH release from cultured sheep pituitary cells. Sheep were sacrificed and pituitary cells cultured in DMEM with 10% fetal bovine serum for 3 days. On day 4, cells were washed and serum-free DMEM added to cells. IL-1alpha and IL-1beta were used at 0.2, 2 and 20 ng/ml and the remaining cytokines at 2, 20 and 200 ng/ml. Neither IL-2 nor INT had effects on basal or on GH-releasing hormone (GRH)-stimulated GH release. TNF inhibited GRH-stimulated GH release (p < 0.05). Both IL-1alpha and IL-1beta stimulated GH release from cultured pituitary cells at all doses tested (p < 0.01). Neither IL-1alpha nor IL-1beta had an effect on GRH-stimulated GH release. IL-1 effects were inhibited by H-89 (p < 0.05; a protein kinase A inhibitor) and by nifedipine (p < 0.05; a calcium channel blocker). Both of these mechanisms are central signal transduction mechanisms mediating GRH-stimulated GH release. IL-1-stimulated GH release is partially inhibited (p < 0.05) by lipoxygenase pathway blockers. Phorbol myristate acetate downregulation of protein kinase C did not alter IL-1-stimulated GH release. IL-1beta increased the content of both GH and GH mRNA in cultured sheep pituitary cells. We conclude that IL-1 produces a strong stimulus to GH release, which is mediated by calcium entry and protein kinase A activation. IL-1 also activates lipoxygenase pathways. This latter pathway as well as calcium entry were shown to mediate LPS stimulation of GH release from cultured pituitary cells. The similarity between IL-1 and LPS signal transduction suggests that LPS may activate pituitary production of IL-1 to produce the stimulus to GH. The lack of inhibitory effects of INT, TNF and IL-2 as opposed to what is seen in the rat may suggest a partial mechanism to explain the different effects of LPS on GH release between sheep and that seen in cattle and rats.     

Effects of interleukins on secretion of luteinizing hormone from ovine pituitary cells

OBJECTIVE: To determine whether cytokines of homologous species might mediate the stimulatory effects of endotoxin on release of luteinizing hormone (LH) from pituitary cells. SAMPLE POPULATION: Cells from pituitary glands collected from 8- to 14-month-old wethers. PROCEDURE: Cells from the anterior pituitary gland were cultured in the presence of recombinant ovine or bovine cytokines (interleukin [IL]-1alpha, IL-1beta, and IL-2), tumor necrosis factor-alpha (TNF), and interferon-gamma (IFN-gamma). Luteinizing hormone that was released into the medium was measured. Cells were also cultured with modulators of signal transduction pathways to evaluate the second messenger system used by IL-1 alpha and IL-1beta. RESULTS: Similar to effects of endotoxin, IL-1alpha and IL-1beta stimulated release of LH. Interleukin 2, TNF, and IFN-gamma did not have a detectable effect on release of LH. Stimulation of LH release by IL-1alpha and IL-1beta required activation of voltage-dependent Ca2+ channels and appeared to involve protein kinase C. CONCLUSIONS: IL-1alpha and IL-1beta may mediate the direct stimulatory effect of endotoxin on release of LH in vitro. Interleukin 2, TNF, and IFN-gamma do not have a direct effect on release of LH; therefore, they do not mediate this effect of endotoxin. CLINICAL RELEVANCE: Stressors, including infection, are often associated with reduced fertility. Infection resulting in endotoxin release, production of interleukins, or both, can lead to direct stimulation of LH release from the pituitary gland. Inopportune release of LH via cytokines may interfere with normal pulsatile release of LH, thereby suppressing gonadal function.     

Effect of luteinizing hormone-releasing hormone on rat adrenocortical cells

The effects of luteinizing hormone-releasing hormone (LH-RH) on the function of rat adrenal cortex were investigated by using dispersed zona glomerulosa (capsular) and zona fasciculata-reticularis (inner) cells. LH-RH increased basal (but not adrenocorticotropic hormone (ACTH)-stimulated) corticosterone secretion of inner cells, without affecting either aldosterone or corticosterone production by capsular cells. LH-RH markedly raised basal (but not ACTH-enhanced) cyclic-AMP release by inner cells. The corticosterone secretagogue action of LH-RH was abolished by the protein kinase A inhibitor H-89. The conclusion is drawn that LH-RH specifically stimulates adrenal glucocorticoid secretion in rats through the activation of the adenylate cyclase signaling pathway.     

Determination of folate transport pathways in cultured rat proximal tubule cells

Deficiency of the vitamin folic acid has recently been linked with increased incidence of neural tube defects and of cardiovascular disease, through elevated plasma homocysteine levels. The kidney has an important role in conserving folate to counteract development of deficiency. Urinary folate excretion is regulated by the degree of reabsorption of folate by the proximal tubule cell. To evaluate an in vitro model for studies of the regulation of urinary folate excretion, the present studies examined the transport of 5-methyltetrahydrofolate (5-CH3-H4PteGlu), the primary form of folate in the glomerular filtrate, by normal rat proximal tubule (RPT) cells in confluent monolayer cultures. Specific binding of 5-CH3-H4PteGlu to the apical membrane was saturable (K(D) = 27 nM), but intracellular transport was not saturated up to 100 nM concentrations. 5-CH3-H4PteGlu transport was decreased 50% by concentrations of folic acid that completely blocked 5-CH3-H4PteGlu binding by the apical folate receptor. Probenecid (10 mM), an anion exchange (reduced folate carrier) inhibitor, reduced 5CH3-H4PteGlu transport by 50% without significantly affecting binding. Aspirin (3 mM) did not alter 5-CH3-H4PteGlu transport, but significantly enhanced the inhibition due to probenecid. Similarly, indomethacin (5 microM) potentiated the inhibition of 5-CH3-H4PteGlu transport by probenecid. These data suggest that RPT cells take up 5-CH3-H4PteGlu by both the folate receptor and the reduced folate carrier, implying a role for both pathways in regulating urinary folate excretion.     

Phenomenon of intrinsic rhythm of luteinizing hormone release from isolated anterior pituitary gland of female rat

The intrinsic nature of rthymic release of luteinizing hormone (LH) of isolated human and rat anterior pituitary gland reported independently by Macro Gambacciani and Xie in 1987 can be more directly demonstrated by a computer programme of Time Series-HSY Hidden Periodic Analytic Approach for continuous monitoring the LH output of the perfusate from a perfusion system with in vitro anterior pituitary of SD female rat. The results are as follows: (1) Under various reproductive conditions the average frequency (min/cycle) and amplitude (ng/ml) of the intrinsic rhythm of LH release were quite different: In proestrous group the frequency and amplitude were the highest, being intermediate in the ovariectomized group and lowest in the lactation group. (2) The intrinsic rhythm of LH release could be changed by either peptide or steroid hormones. In proestrous group with 30 min of gonadotropin-releasing hormone (GnRH), stimulation would reduce both frequency and amplitude. In case of lactation, the frequency was unchanged, but amplitude lowered, while in the ovariectomized rat pituitary, the 30 min GnRH stimulation decreased the frequency of release only. The intrinsic rhythm of the LH release could also be influenced by steriod hormones (Ru486 and Anordrin). With 120 min before removal of the anterior pituitary gland the rats receiving i.m. injection of Ru486 (2 mg/kg bw) or Anordrin (2 mg/kg), the results showed that Ru486 decreased frequency, while Anordrin decreased only the frequency to a less extent, both without amplitude affected. (3) Verapamil and EGTA added to the perfusion system did not abolish but only decreased the rhythmic phenomenon by using proestrous pitutary. This suggests that participation of Ca2+ may take place in the intrinsic release of LH. The above results indicated that the intrinsic rhythm of LH release of isolated anterior pituitary gland is different from various reproductive hormonal conditions and capable of being modified by exogenous hormones. The physiological function of the intrinsic rhythm of LH release of anterior pituitary gland remains to be elucidated.     

The effect of chronic luteinizing hormone treatment on adult rat Leydig cells

OBJECTIVES: In a preliminary pilot study of 30 treatments in 26 patients with osteonecrosis of the jaws and chronic disabling facial pain, our specific aim was to determine whether, to what degree, and how safely therapy of hypofibrinolysis and thrombophilia would ameliorate the chronic pain associated with osteonecrosis of the mandible and maxilla. STUDY DESIGN: Thrombophilia was treated with Coumadin (DuPont) in 10 patients; hypofibrinolysis was treated with Winstrol (Sanofi-Winthrop) in 20 patients, including 4 who had mixed thrombophilia and hypofibrinolysis and had previously been treated with Coumadin. The initial treatment period was targeted to be 4 months. Each patient was asked to keep a daily written pain-relief numeric rating score and side-effects diary and to provide a summary pain-relief numeric rating score and side effects compilation for the total treatment period. RESULTS: There were 4 men and 22 women in the study group; their mean age was 49 +/- 11 years. The mean onset of their osteonecrosis pain was at age 45 +/- 12 years, and the mean duration of their facial pain prior to therapy was 4.5 +/- 4.2 years. Ten patients had one or more thrombophilic traits (there were two patients with protein C deficiency, five with resistance to activated protein C and/or the mutant Factor V Leiden gene, and four with high anticardiolipin antibodies). The 10 patients who were thrombophilic were treated with Coumadin (the international normalized ratio was targeted to 2.5-3.0) for 22 +/- 9 weeks. By self-reported pain-relief numeric rating scores, 6 of the 10 patients with thrombophilia (60%) had > or = 40% pain relief, 2 (20%) had no change, and 2 (20%) had increased pain (30% and 80% worse). Nine of the 10 patients with thrombophilia (90%) had no Coumadin-related side effects; 1 patient (10%) stopped Coumadin therapy (after 28 weeks) because of nosebleeds. Winstrol (6 mg per day) was used for 16 +/- 9 weeks in 20 patients with hypofibrinolysis, some of whom had one or more hypofibrinolytic traits (10 had high levels of plasminogen activator/inhibitor activity, usually accompanied by low stimulated tissue plasminogen activator activity; 13 had high Lp[a] lipoprotein). Of these 20 patients with hypofibrinolysis, 9 patients (45%) had > or = 40% pain relief, 3 patients (15%) had 20% to 30% relief, 5 patients (25%) had no improvement, and 3 patients (15%) had increased pain (30% worse, 60% worse, and 70% worse). Six of the 20 patients with hypofibrinolysis (30%) had no Winstrol-related side effects, while 14 (70%) had side effects that could be attributed to Winstrol, including weight gain, peripheral edema, increased facial and body hair, and acne--all of which were reversed within 6 weeks of stopping Winstrol therapy. CONCLUSIONS: We postulate that thrombophilia and hypofibrinolysis lead to impaired venous circulation and venous hypertension of the mandible/maxilla with subsequent development of osteonecrosis and chronic facial pain. In many patients, facial pain can be ameliorated by treating the pathogenetic coagulation defects with Coumadin or Winstrol. Large, double-blind, placebo-controlled crossover studies will be required in the future to validate these preliminary results and to determine whether pain relief with Coumadin or Winstrol justifies the risks and side effects associated with these medications, especially for long-term use, in osteonecrosis of the jaws.     

Myoglobin inhibits proliferation of cultured human proximal tubular (HK-2) cells

Following nephrotoxic injury, renal repair is dependent on tubular regeneration. In the case of myoglobinuric acute renal failure (ARF), persistence of myoglobin within tubular cells, or sublethal injury sustained at the height of exposure to it, might retard this process. To test this hypothesis, a human proximal tubular cell line (HK-2) was cultured for 24 hours in the absence or presence of clinically relevant myoglobin concentrations (0.5, 1, 2, 4 mg/ml). Immediately following myoglobin removal, lethal cell injury (vital dye uptake), lipid peroxidation, and DNA damage (alkaline unwinding assay) were assessed. The extent of cell proliferation was estimated over the next four days by a tetrazolium based (MTT) assay and by determining total intracellular LDH. Myoglobin's effects on protein and DNA synthesis were also assessed (35S-methionine and bromodeoxyuridine incorporation, respectively). Myoglobin induced dose-dependent lipid peroxidation (malondialdehyde generation) and cell death (up to 80% vital dye uptake with the 4 mg/ml challenge). Although 1 mg/ml myoglobin caused no cell death, it induced nearly complete growth arrest. This lasted for approximately three days following myoglobin removal from the media. Neither of two control proteins (albumin; lysozyme) nor a second nephrotoxin (gentamicin; 1 mg/ml) reproduced this effect. The 1 mg/ml myoglobin challenge caused an 80 to 90% depression in protein and DNA synthesis. It also induced significant DNA damage, as assessed by the alkaline unwinding assay (P < 0.01). Iron chelation therapy (deferoxamine) mitigated myoglobin-induced cell killing. However, its addition following myoglobin loading worsened HK-2 outgrowth by exerting a direct anti-proliferative effect. These results indicate that: (1) sublethal myoglobin toxicity can induce transient proximal tubular cell growth arrest, potentially slowing recovery from ARF; (2) this effect correlates with, and could result from, heme-induced DNA damage and a blockade in DNA/protein synthesis; and (3) deferoxamine can inhibit proximal tubular cell proliferation. This possibility needs to be considered in designing clinical trials with DFO for myohemoglobinuric ARF.     

Enhancement of secretagogue-induced adrenocorticotropic hormone release from cultured sheep anterior pituitary cells by recombinant ovine interleukin 1

Interaction between protein disulfide isomerase, possessing not only isomerase but also chaperone-like activity, and olygomeric enzyme, GAPDH, has been studied using technique of immobilization on insoluble support. PDI dimers bound to CNBr-activated Sepharose were shown to possess high TPOR activity as well as the ability to reactivate lysozyme. Immobilized PDI was not found to interact neither with soluble tetrameric GAPDH, nor with soluble denatured GAPDH. However, soluble PDI binds effectively to immobilized GAPDH monomers; Kd was found to be 3.7 x 10(-6) M, stoichiometry 0.824 mole PDI monomers per mole GAPDH monomers. Immobilized GAPDH tetramers do not interact with PDI. These observations are also confirmed by the data on electrophoresis of proteins bound to immobilized GAPDH monomers and tetramers. The ability of PDI to interact with denatured protein form, but not with the native one, is considered to be evidence of chaperone-like activity of the enzyme.     

Stimulation by urocortin of growth hormone (GH) secretion in GH-producing human pituitary adenoma cells

Urocortin (Ucn) possesses high homology with CRH and is considered to be a ligand to type-2 CRH receptor. We investigated the effect of Ucn on hormone release from cultured GH-producing human pituitary adenoma cells in vitro. GH-producing human pituitary adenoma cells were superfused on a Sephadex G-25 column. Both Ucn (10 nM) and CRH (10 nM) elicited an increase in GH release from the pituitary adenoma cells in one patient with acromegaly. In contrast, GH release from the pituitary adenoma cells was stimulated by Ucn but not by CRH in the other patient with acromegaly. These preliminary findings suggest that type-2 CRH receptors are expressed in some population of GH-producing human pituitary adenoma cells and that Ucn might be involved in GH secretion from tumorous tissues in patients with acromegaly.     

Regulation of hippocampal gonadotropin releasing hormone (GnRH) receptor mRNA and GnRH-stimulated inositol phosphate production by gonadal steroid hormones

Cooperation in the action of agonists suggests that there are multiple binding sites on 5-hydroxytryptamine3 (5-HT3) receptors. The purpose of this study was to characterize these binding sites and their interactions on both native and cloned 5-HT3 receptors. The affinities of competitive 5-HT3 receptor antagonists were similar regardless of whether the receptors were labeled with [3H]RS-42358, [3H]granisetron, or 1-(m-[3H]chlorophenyl)biguanide ([3H]mCPG). By contrast, the affinities of the agonists 5-HT, mCPG, and phenylbiguanide were approximately 10-fold higher when the receptors were labeled with [3H]mCPG. The dissociation of [3H]mCPG, [3H]RS-42358, and [3H]RS-25259, but not [3H]granisetron, from both cloned and native 5-HT3 receptors was markedly slower in the presence of 5-HT or 2-methyl-5-HT than in the presence of antagonists such as RS-42358. This suggests that the binding of these agonists to unoccupied sites on the receptor can increase the receptor's affinity for prebound ligands and thereby slow their dissociation. These data support previous indications of positive cooperation among multiple binding sites on both native and cloned 5-HT3 receptors, and they extend this idea by demonstrating that agonists can modify the interaction of some, but not all, antagonists with the receptor.     

Immunocytochemical evidence that luteinizing hormone (LH) and follicle stimulating hormone (FSH) are present in the same cell type in the rhesus monkey pituitary gland

Antisera to oLHbeta subunits were used to identify the gonadotrophic cells in partes distalis and tuberalis of the rhesus monkey pituitary gland. The same cell type in pituitary glands obtained from male and female rhesus monkeys stained with both antisera. Immunocytochemical staining was observed in PAS positive cells that were randomly dispersed throughout the entire pars distalis. The gonadotrophs did not react with antisera to either hTSHbeta or oACTH. These observations indicate that only one gonadotrophic cell type is present in the primate pituitary gland.     

Immunological detection of membrane-associated human luteinizing hormone correlates with gene expression in cultured human cancer and fetal cells

We have demonstrated the expression of membrane-associated hCG and its subunits and fragments by cells from 78 human cancer cell lines of different types and origins, indicating that such expression is a common phenotypic characteristic of cultured human malignant cells. Because human (h) LH beta has 80% homology with hCG beta and is coded by one of the seven genes in the gene cluster located in chromosome 19, it was important to determine whether hLH and its beta-subunit are also expressed as membrane-associated proteins by cells from human cancer cell lines. Thus, 11 cancer cell lines of different types and origins were adapted to grow in serumless medium, with Nutridoma-HU or SP as serum substitute, and analyzed by flow cytometry using two monoclonal antibodies directed to different conformational epitopes of intact hLH and a monoclonal antibody reacting with an epitope of hLH beta-free. The cells were also analyzed simultaneously for the expression of hCG and its subunits and fragments. Determination of translatable levels of hLH beta and hCG beta messenger RNAs (mRNAs) was performed in cells from some of the cancer cell lines, including the JEG-3 choriocarcinoma cell line, and in cells from a human fetal lung cell line. The analytical flow cytometry studies showed that in addition to the expression of membrane-associated hCG in all of its forms, expression of membrane-associated intact (holo) hLH and its free beta-subunit occurred in every case. These findings were corroborated by the presence of translatable levels of hLH beta and hCG beta mRNAs in all of the cancer cell lines analyzed, indicating that the expression of these membrane-associated glycoproteins is a phenotypic characteristic of human cancer cells and that the activation of the hCG beta-hLH beta gene cluster is nonselective. The presence of translatable levels of hCG beta-hLH beta mRNAs in the cultured human fetal lung cells punctuates once more the in vivo and in vitro biochemical similarities between fetal and cancer cells.     

Effects of the opioid antagonist naltrexone-estrone azine on the luteinizing hormone-releasing hormone induced release of luteinizing hormone from the pituitary glands of ovariectomized rats

The effects were studied of in vivo administration of the new opioid antagonist-estrogen hybrid, naltrexone-estrone azine (EH-NX), on subsequent luteinizing hormone-releasing hormone (LHRH)-stimulated luteinizing hormone (LH) release by the pituitary gland in vitro. It is well known that administration of estrogen exerts negative and positive effects on the pituitary LH response to LHRH, respectively after short-term and long-term treatment. Rats were injected subcutaneously with either 17 beta-estradiol-3-benzoate (EB), EH-NX or oil on days 18 and 19 (long-term treatment), and on day 21 (short-term treatment) following ovariectomy. Twenty minutes later the animals were killed and the pituitary glands were incubated in the presence of LHRH (1000 ng/ml) for 4 h. Whereas short-term treatment with EB on day 21 did not affect LH release in vitro, EH-NX significantly decreased the pituitary LH response to LHRH in oil pretreated rats. This inhibitory effect was partially blocked by the opioid antagonist naltrexone. After long-term EB or EH-NX, followed by short-term oil treatment, the pituitary LH response to LHRH was increased considerably, compared to the long-term oil controls. These observations demonstrate that the opioid antagonist estrogen hybrid EH-NX has estrogenic activity at the level of the pituitary gland. This hybridized drug is more effective in time than EB and an equimolar amount of EH (estrone hydrazone) to induce the negative estrogenic effect.     

Differential effects of intraventricular luteinizing hormone releasing hormone (LH-RH) and norepinephrine on electrical activity of the arcuate nucleus in the proestrous rat

Effects of intraventricular infusions of LH-RH and norepinephrine (NE) on the electrical activity of the arcuate nucleus were investigated in normally cycling proestrous rats. Under urethane anesthesia, recordings were made of amplitude-discriminated multiple unit spike activity and integated multiunit activity (MUA) in parallel with cortical EEG. Control infusions of saline (2 microliter, isotonic, pH 5.5) were ineffectual, but LH-RH (0.5 microgram) induced a significant increase in both multiunit spike activity and integrated MUA. While the response appeared to be continuous, statistical analysis revealed 2 phases: a quick rise which persisted for approximately 5 min, followed 15 min later by a longer-lasting elevation in activity. The onset of the 2nd increase corresponded with the attainment of peak values of pituitary LH output. Subsequent treatment with 20 microgram NE, on the other hand, resulted in a marked depression of activity. The fact that NE depresses arcuate neuronal activity at dose levels which cause the release of LH and that LH-RH increases activity within the same population of neurons, while possibly mediating an 'ultrashort-loop' negative feedback effect, suggest that this responsive component of the arcuate nucleus, perphaps the tuberoinfundibular dopaminergic system of neurons, is inhibitory to LH release.     

Follicle-stimulating hormone (FSH) regulates the expression of FSH receptor messenger ribonucleic acid in cultured Sertoli cells and in hypophysectomized rat testis

FSH acts on Sertoli cells via interaction with a transmembrane receptor (FSHr). Control of expression of the receptor is surely a factor in the regulation of the action of FSH. The regulation of FSHr by FSH and testosterone was studied both in culture and in vivo. Sertoli cells from 18- to 20-day-old male rats were cultured in the presence of 25 ng/ml ovine (o) FSH. At 8 h after addition of FSH, expression of FSHr mRNA decreased significantly. Addition of FSH and actinomycin D to cells did not result in a further decrease in FSHr mRNA levels, suggesting that FSH does not alter turnover of FSHr mRNA. Treatment of cells with 40 ng/ml testosterone did not have any significant effect on the expression of FSHr mRNA. Hypophysectomy of 20-day-old male rats resulted in an increase in expression of FSHr mRNA as compared to that in sham-hypophysectomized animals. This increase was measured at 24 h posthypophysectomy and was maintained at 72 h after surgery. Injection of rats with 0.2 U oFSH at 48 h posthypophysectomy resulted in a reduction in FSHr mRNA when compared to the levels in hypophysectomized rats. Treatment with 2 mg testosterone propionate had no effect on FSHr mRNA levels. The findings confirm that FSH plays an important role in regulating mRNA expression of the FSHr in Sertoli cells in culture and show for the first time that FSHr mRNA is regulated in vivo by FSH in the immature rat testis.     

Downregulation of protein kinase C levels leads to inhibition of GnRH-stimulated gonadotropin secretion from dispersed pituitary cells of goldfish

In spring 1992 the Austrian Parliament has enacted a new law dealing with reproductive medicine. The 'Act on medically assisted conception' contains provisions which totally prohibit particular methods of assisted fertilization (such as embryo or egg donation). The main goal of the act, however, is to regulate procreative medicine and to amend the Austrian General Civil Code: the parents-to-be are now considered to have the legal rights and responsibilities of biological parents in any case.