Hepatically derived selenoprotein P is a key factor for kidney but not for brain selenium supply.

Liver-specific inactivation of Trsp, the gene for selenocysteine tRNA, removes SePP (selenoprotein P) from plasma, causing serum selenium levels to fall from 298 microg/l to 50 microg/l and kidney selenium to decrease to 36% of wild-type levels. Likewise, glutathione peroxidase activities decreased in plasma and kidney to 43% and 18% respectively of wild-type levels. This agrees nicely with data from SePP knockout mice, supporting a selenium transport role for hepatically expressed SePP.

Real time RT-PCR analysis of thyroglobulin mRNA in peripheral blood in patients with congenital athyreosis and with differentiated thyroid carcinoma after stimulation with recombinant human thyrotropin.

Objective: Thyroglobulin (Tg), measured by immunometric assay, is the most sensitive and widely used clinical marker for thyroid cancer progression and relapse. However, these Tg determinations are of limited sensitivity and susceptible to interference by Tg autoantibodies. As a possible diagnostic alternative, we tested a real time RT-PCR protocol to determine Tg mRNA levels in peripheral blood.

Endocrine active compounds affect thyrotropin and thyroid hormone levels in serum as well as endpoints of thyroid hormone action in liver, heart and kidney.

To assess interference with endocrine regulation of the thyroid axis, rats (female, ovariectomised) were treated for 12 weeks with the suspected endocrine active compounds (EAC) or endocrine disrupters (ED) 4-nonylphenol (NP), octyl-methoxycinnamate (OMC) and 4-methylbenzylidene-camphor (4-MBC) as well as 17beta-estradiol (E2) and 5alpha-androstane-3beta,17beta-diol (Adiol) on the background of a soy-free or soy-containing diet, and endpoints relevant for regulation via the thyroid axis were measured. Thyrotropin (TSH) and thyroid hormone (T4, T3) serum levels were altered, but not in a way consistent with known mechanisms of feedback regulation of the thyroid axis. In the liver, malic enzyme (ME) activity was significantly increased by E2 and Adiol, slightly by OMC and MBC and decreased by soy, whereas type I 5'-deiodinase (5'DI) was decreased by all treatments.

Selenium and selenoproteins in mammals: extraordinary, essential, enigmatic.

Selenium (Se), once known only for its potential toxicity, is now well established as an essential trace element for mammals. Insufficient Se intake predisposes to and manifests in a variety of diseases. Recent studies have proven that it is the synthesis of selenocysteine (Sec)-containing proteins, designated selenoproteins, which represents an essential prerequisite for regular development and a long and healthy life.

The neurobiology of selenium: lessons from transgenic mice.

The brain represents a privileged organ with respect to selenium (Se) supply and retention. It contains high amounts of this essential trace element, which is efficiently retained even in conditions of Se deficiency. Accordingly, no severe neurological phenotype has been reported for animals exposed to Se-depleted diets.

Efficient selenium transfer from mother to offspring in selenoprotein-P-deficient mice enables dose-dependent rescue of phenotypes associated with selenium deficiency.

Mice deficient in selenoprotein P exhibit a disturbed selenium distribution and reduced activities of other selenoenzymes and display defects in growth and motor co-ordination. We have normalized selenoenzyme activities and rescued the phenotype of mutant mice by supplementing their nursing mothers with sodium selenite. Our results indicate that selenium from inorganic sources can be transferred efficiently via mother's milk to the developing offspring in a form that is both highly bioavailable by target tissues and yet sufficiently safe to prevent overdosages.

Gene disruption discloses role of selenoprotein P in selenium delivery to target tissues.

Selenoprotein P (SePP), the major selenoprotein in plasma, has been implicated in selenium transport, selenium detoxification or antioxidant defence. We generated SePP-knockout mice that were viable, but exhibited reduced growth and developed ataxia. Selenium content was elevated in liver, but low in plasma and other tissues, and selenoenzyme activities changed accordingly.

Effect of endotoxin on expression of TNF receptors and transport of TNF-alpha at the blood-brain barrier of the rat.

The transport mechanism mediating brain uptake of tumor necrosis factor (TNF)-alpha has been studied. When (125)I-labeled rat TNF-alpha was used in internal carotid artery perfusions in rats, the cytokine showed transcytosis through the blood-brain barrier in intact form (permeability-surface area product 0.34 +/- 0.

Molecular characterization of a puromycin-insensitive leucyl-specific aminopeptidase, PILS-AP.

The family M1 of Zn-dependent aminopeptidases comprises members of closely related enzymes which are known to be involved in a variety of physiologically important processes. On the basis of two highly conserved peptide motifs, we have identified a new member of this family by PCR amplification and cDNA-library screening. The longest ORF encodes a protein of 930 residues.

Prolactin-releasing peptides do not stimulate prolactin release in vivo.

The prolactin (PRL)-releasing activity of the novel prolactin-releasing peptides (PrRPs) was studied in vivo using male and lactating female rats. Whereas thyrotropin-releasing hormone effectively stimulated PRL and thyrotropin release as expected, PrRP in both animal models neither stimulated PRL secretion nor affected the release of other pituitary hormones. At the anterior pituitary level, in situ hybridization (ISH) histochemistry and Northern blot analysis revealed significantly higher expression levels of PrRP receptor (UHR-1) transcripts in female compared to male rats but not between lactating and nonlactating animals.

Human TRH-degrading ectoenzyme cDNA cloning, functional expression, genomic structure and chromosomal assignment.

Thyrotropin-Releasing Hormone (TRH) is an important extracellular signal substance that acts as a stimulator of hormone secretion from adenohypophyseal target cells and fulfills many criteria for the function of a neuromodulator/neurotransmitter within the central and peripheral nervous systems. The inactivation of TRH-signals is catalysed by a highly specific ectoenzyme. Here, we characterize the human TRH-degrading ectoenzyme (TRH-DE) by primary sequence, functional expression, genomic structure and chromosomal assignment.

Expression and hormonal regulation of coactivator and corepressor genes.

Steroid/thyroid/retinoid receptors are members of the nuclear receptor superfamily and ligand-inducible transcription factors. These receptors modulate transcription of various cellular genes, either positively or negatively, by interacting with specific hormone-response elements located in the target gene promoters. Recent data show that nuclear receptors enhance or inhibit transcription by recruiting an array of coactivator and corepressor proteins to the transcription complex.

Regulation of the adenohypophyseal thyrotropin-releasing hormone-degrading ectoenzyme by estradiol.

TRH is inactivated by the TRH-degrading ectoenzyme, a TRH-specific metallopeptidase. At the pituitary level, this enzyme is stringently regulated by thyroid hormones. We describe here gender-related differences and the effect of estradiol (E2) on the expression of this enzyme in the anterior pituitary.

Thyrotropin-releasing hormone gene expression by anterior pituitary cells in long-term cultures is influenced by the culture conditions and cell-to-cell interactions.

It has been suggested that TRH, synthesized by anterior pituitary (AP) cells in long-term monolayer cultures, may act as a paracrine or autocrine regulator. Because local control through messenger molecules depends on the cellular microenvironment, we were interested in studying the synthesis of TRH by AP cells in different culture systems and under various conditions. When AP cells were cultured as monolayers in medium containing 10% FCS for long periods of time (up to 3 weeks), a considerable increase in TRH content and prepro-TRHmessengerRNA (preproTRHmRNA) levels could be demonstrated by RIA and Northern blot analysis, whereas the cellular content of the TRH-like peptide pyroGlu-Glu-Pro-NH2 decreased with time in culture to undetectable levels.

Genomic organization and promoter structure of the human EXT1 gene.

Hereditary predisposition to multiple exostoses is a genetically heterogeneous disease. Recently, we have reported the identification of the EXT1 gene on human chromosome 8. We have now isolated a cDNA clone from a human adult lung cDNA library and have determined the genomic organization and promoter structure of the EXT1 gene.

Thyroid hormones rapidly and stringently regulate the messenger RNA levels of the thyrotropin-releasing hormone (TRH) receptor and the TRH-degrading ectoenzyme.

The responsiveness of adenohypophyseal target cells for the hypothalamic neuropeptide TRH is known to change depending on the hormonal and physiological conditions of the organism. We describe here the effects of thyroid hormones on the transcript levels of the TRH receptor, the TRH-degrading ectoenzyme, and TSH in rat pituitary, as revealed by Northern blot analysis. After a single injection of T3 (30 micrograms/100 g BW), the transcript levels of the TRH receptor decreased transiently, reaching 35% of control values 4 h after injection, and returned to basal levels within 24 h.

Rapid stimulation of type I 5'-deiodinase in rat pituitaries by 3,3',5-triiodo-L-thyronine.

The negative feedback control of thyrotropin production by the anterior pituitary involves local 5'-deiodination of L-thyroxine (L-T4) to the active thyroid hormone 3,3',5-triiodo-L-thyronine (T3) by two 5'-deiodinase isozymes which are distinctly regulated by thyroid hormone. T3 rapidly increased steady-state mRNA levels and activity of type I iodothyronine-5'-deiodinase (5'DI) in rat anterior pituitary and in reaggregate cultures of anterior pituitaries. Type II 5'-deiodinase activity determined in parallel with 3,3',5-triiodo-L-thyronine (rT3) as substrate was markedly lower than that of 5'DI.

Cloning of a cDNA encoding an ectoenzyme that degrades thyrotropin-releasing hormone.

Thyrotropin-releasing hormone (TRH) is an important extracellular signal substance that acts as a hypothalamic-releasing factor, which stimulates the release of adenohypophyseal hormones and functions as a neurotransmitter/neuromodulator in the central and peripheral nervous system. The inactivation of TRH after its release is catalyzed by an ectoenzyme localized preferentially on neuronal cells in the brain and on lactotrophic pituitary cells. This enzyme exhibits a very high degree of substrate specificity as well as other unusual properties.