LHRH interaction with Zn(II) ions

Luteinizing hormone-releasing hormone (LHRH), a hypothalamic neurohormone, forms a complex with Zn ions in solution. In order to explain the structure of this complex, the stability constants of Zn(II) complexes of LHRH and also pyroglutamyl-histidine-methylester, N-acetyl-histamine, and N-acetyl-histidine were established with the use of potentiometric technique. The nuclear magnetic resonance spectroscopy shows that the mode of coordination of Zn(II) to LHRH consists of binding to the imidazole nitrogen and the peptide oxygen of the His-Trp bond.     

Molecular and crystal structure of Nα-(9-fluorenyl)- methoxycarbonyl-L-ornithine hydrochloride diethyl ether solvate

Summary The solid-state conformation of the first N-protected ornithine derivative has been established by X-ray analysis. The hydrochloride of N^α-(9-fluorenyl)methoxycarbonyl-l-ornithine crystallises as diethyl ether solvate. The backbone (ω₀ ϕ, ψ χ¹) torsion angles are (174.9°,–84.0°, 145.9°,–171.0°). The conformation of the urethane amide bonds istrans. The ornithine aliphatic side chain adopts preferred fully extended conformation which is stabilised by the hydrogen bonding of the-NH ₃ ⁺ group to the diethyl ether molecule, carboxyl group and Cl⁻ anions.     

Behavioural effects of luteinizing hormone-releasing hormone (LHRH) in rats.

Behavioural effects of intracerebroventricularly-injected (icv) LHRH were studied in female rats. Locomotor and exploratory activities as well as irritability were determined. A pronounced inhibitory effect of 10 micrograms doses of LHRH was found. At 100 micrograms doses of LHRH, barrel behaviour was observed. We conclude that LHRH can modify the activity of central serotonergic receptors in rats.     

Molecular and crystal structure of Nα-(9-fluorenyl)- methoxycarbonyl-L-ornithine hydrochloride diethyl ether solvate

The solid-state conformation of the first N-protected ornithine derivative has been established by X-ray analysis. The hydrochloride of N-(9-fluorenyl)methoxycarbonyl-L-ornithine crystallises as diethyl ether solvate. The backbone (₀, , , ¹) torsion angles are (174.9°, –84.0°, 145.9°, –171.0°). The conformation of the urethane amide bond is trans. The ornithine aliphatic side chain adopts preferred fully extended conformation which is stabilised by the hydrogen bonding of the –NH₃ ⁺ group to the diethyl ether molecule, carboxyl group and Cl^- anions.     

Parathyroid hormone induces hepatic production of bioactive interleukin-6 and its soluble receptor

Interleukin-6 (IL-6) is an important mediator of parathyroid hormone (PTH)-induced bone resorption. Serum levels of IL-6 and its soluble receptor (IL-6sR) are regulated in part by PTH. The PTH/PTH-related protein type 1 receptor is highly expressed in the liver, and in the current study we investigated whether the liver produces IL-6 or IL-6sR in response to PTH. Perfusion of the isolated rat liver with PTH-(1-84) stimulated rapid, dose-dependent production of bioactive IL-6 and the IL-6sR. These effects were observed at near physiological concentrations of the hormone such that 1 pM PTH induced hepatic IL-6 production at a rate of approximately 0.6 ng/min. In vitro, hepatocytes, hepatic endothelial cells, and Kupffer cells, but not hepatic stellate cells, were each found to produce both IL-6 and IL-6sR in response to higher (10 nM) concentrations of PTH. Our data suggest that hepatic-derived IL-6 and IL-6sR contribute to the increase in circulating levels of these cytokines induced by PTH in vivo and raise the possibility that PTH-induced, liver-derived IL-6 may exert endocrine effects on tissues such as bone.     

Acetylation of methyl 5-amino-1H-[1,2,4]triazole-3-carboxylate

Acetylation with acetic anhydride of methyl 5-amino-1H-[1,2,4]triazole-3-carboxylate, one of the hetareneamino acids, was studied using HPLC, H NMR, FTIR and GC-MS. The compound has a significantly decreased susceptibility to acetylation compared to 5-amino-1H-[1,2,4]triazole itself. Two isomeric diacetylated products were found.     

Increased LH and FSH release from the anterior pituitary of ovariectomized rat, in vivo, by copper-, nickel-, and zinc-LHRH complexes.

The effect of Cu2+, Ni2+, Zn2+ and their complexes with LHRH on the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH) was estimated in in vivo experiments with the use of the method proposed by Ramirez and McCann. Ovariectomized, estradiol, and progesterone pretreated rats were injected intravenously either with LHRH alone, a metal ion alone, a mixture of metal and hormone, or a metal-LHRH complex. A metal alone or a mixture of it with LHRH did not affect gonadotropin release at all or no more than LHRH alone. However, the complex of Cu2+ with LHRH brought about a high release of LH and even higher release of FSH. This indicates that copper complex is more effective than metal-free LHRH. The nickel complex showed a similar although lesser effect. The zinc complex had similar potency to free LHRH though higher FSH-releasing ability was noticed. We conclude that copper-, nickel-, and zinc-LHRH complexes were more potent than the peptide hormone itself and promoted the FSH release in the ovariectomized, estradiol, and progesterone pretreated rats.     

Metal complexes of luteinizing hormone-releasing hormone (LHRH). potentiometric and spectroscopic studies

The results are reported of a potentiometric and spectroscopic study of the H+, Cu2+, and Ni2+ complexes of luteinizing hormone-releasing hormone (LHRH, HL) at 25 degrees C and an ionic strength 0.10 mol dm-3 (KNO3), since there is much evidence that the in vivo release of LHRH is influenced by the concentration of copper ions. With Cu2+ the hormone has been shown to behave similarly to the thyrotropin releasing factor, forming a very stable [CuH-1L] complex involving coordination of three nitrogen donors: the Nim atom of the imidazole side chain and the two amido-N atoms of the pyroglutamylhistidyl unit. With Ni2+, coordination proceeds differently to give four nitrogen coordination.